diff --git a/include/asyncpp/core.h b/include/asyncpp/core.h
index 60e76d1..1a4db45 100644
--- a/include/asyncpp/core.h
+++ b/include/asyncpp/core.h
@@ -5,14 +5,3 @@
 #include "core/result.h"
 #include "core/stream.h"
 #include "core/task.h"
-
-#include "core/result.inl"
-#include "core/stream.inl"
-
-#include "core/future/map.inl"
-#include "core/future/lazy.inl"
-#include "core/future/and_then.inl"
-
-#ifdef asyncpp_timing
-#include "core/future/timeout.inl"
-#endif
diff --git a/include/asyncpp/core/future.h b/include/asyncpp/core/future.h
index 50fd9fd..13b1ae8 100644
--- a/include/asyncpp/core/future.h
+++ b/include/asyncpp/core/future.h
@@ -1,90 +1,11 @@
 #pragma once
 
-#include <type_traits>
+#include "future/future.h"
 
-#include "misc.h"
-#include "result.h"
-#include "future.pre.h"
+#include "future/map.inl"
+#include "future/lazy.inl"
+#include "future/and_then.inl"
 
-#include "future/map.h"
-#include "future/lazy.h"
-#include "future/and_then.h"
-
-namespace asyncpp
-{
-
-    template<
-        typename T_value,
-        typename T_derived>
-    struct base_future
-        : public tag_future
-    {
-    public:
-        using value_type    = T_value;
-        using result_type   = future_result<value_type>;
-        using derived_type  = T_derived;
-        using this_type     = base_future<value_type, derived_type>;
-
-    public:
-        /**
-         * @brief Transform the result of this future.
-         */
-        template<
-            chaining_mode X_mode = copy,
-            typename X_lambda>
-        inline auto map(X_lambda&& p_lambda) &;
-
-        /**
-         * @brief Transform the result of this future.
-         */
-        template<
-            chaining_mode X_mode = move,
-            typename X_lambda>
-        inline auto map(X_lambda&& p_lambda) &&;
-
-    public:
-        /**
-         * @brief Execute the given lambda after the future is finished and
-         *        wait for the future returned by the lambda.
-         */
-        template<
-            chaining_mode X_mode = copy,
-            typename X_lambda>
-        inline auto and_then(X_lambda&& p_lambda) &;
-
-        /**
-         * @brief Execute the given lambda after the future is finished and
-         *        wait for the future returned by the lambda.
-         */
-        template<
-            chaining_mode X_mode = move,
-            typename X_lambda>
-        inline auto and_then(X_lambda&& p_lambda) &&;
-
-    #ifdef asyncpp_timing
-    public:
-        /**
-         * @brief Throw an execption if the timeout has passed.
-         *
-         * This method is only enabled if timer.h is included before.
-         */
-        template<
-            chaining_mode X_mode = copy,
-            typename X_base,
-            typename X_ratio>
-        inline auto timeout(const duration<X_base, X_ratio>& p_timeout) &;
-
-        /**
-         * @brief Throw an execption if the timeout has passed.
-         *
-         * This method is only enabled if timer.h is included before.
-         */
-        template<
-            chaining_mode X_mode = move,
-            typename X_base,
-            typename X_ratio>
-        inline auto timeout(const duration<X_base, X_ratio>& p_timeout) &&;
-    #endif
-    };
-
-}
+#ifdef asyncpp_timing
+#include "future/timeout.inl"
+#endif
diff --git a/include/asyncpp/core/future/and_then.h b/include/asyncpp/core/future/and_then.h
deleted file mode 100644
index e9ed584..0000000
--- a/include/asyncpp/core/future/and_then.h
+++ /dev/null
@@ -1,56 +0,0 @@
-#pragma once
-
-#include <memory>
-
-#include "../future.pre.h"
-
-namespace asyncpp {
-namespace __future {
-
-    template<
-        typename T_future,
-        typename T_lambda>
-    struct and_then_future final :
-        public base_future<
-            decltype(std::declval<T_lambda>()(std::declval<typename std::decay_t<T_future>::value_type>())),
-            and_then_future<T_future, T_lambda>
-        >
-    {
-    public:
-        using lambda_type               = T_lambda;
-        using first_future_type         = T_future;
-        using first_value_type          = typename std::decay_t<first_future_type>::value_type;
-        using second_future_type        = decltype(std::declval<lambda_type>()(std::declval<first_value_type>()));
-        using second_future_type_ptr    = std::unique_ptr<second_future_type>;
-        using value_type                = typename second_future_type::value_type;
-        using this_type                 = and_then_future<value_type, lambda_type>;
-        using base_future_type          = base_future<value_type, this_type>;
-        using result_type               = typename base_future_type::result_type;
-
-    private:
-        lambda_type             _lambda;
-        first_future_type       _first;
-        second_future_type_ptr  _second;
-
-    public:
-        /**
-         * @brief Constructor.
-         */
-        template<
-            typename X_future,
-            typename X_lambda>
-        inline and_then_future(
-            X_future&& p_outer,
-            X_lambda&& p_lambda);
-
-        inline and_then_future(and_then_future &&) = default;
-        inline and_then_future(and_then_future const &) = default;
-
-    public: /* future */
-        /**
-         * @brief Poll the result from the future.
-         */
-        inline result_type poll();
-    };
-
-} }
diff --git a/include/asyncpp/core/future/and_then.inl b/include/asyncpp/core/future/and_then.inl
index 2a611a0..ee31a54 100644
--- a/include/asyncpp/core/future/and_then.inl
+++ b/include/asyncpp/core/future/and_then.inl
@@ -1,50 +1,77 @@
 #pragma once
 
-#include "and_then.h"
-#include "../future.h"
+#include <memory>
+
+#include "future.h"
 
 namespace asyncpp {
 namespace __future {
 
-    /* and_then_future */
-
     template<
         typename T_future,
         typename T_lambda>
-    template<
-        typename X_future,
-        typename X_lambda>
-    and_then_future<T_future, T_lambda>
-        ::and_then_future(
+    struct and_then_future final :
+        public base_future<
+            decltype(std::declval<T_lambda>()(std::declval<typename std::decay_t<T_future>::value_type>())),
+            and_then_future<T_future, T_lambda>
+        >
+    {
+    public:
+        using lambda_type               = T_lambda;
+        using first_future_type         = T_future;
+        using first_value_type          = typename std::decay_t<first_future_type>::value_type;
+        using second_future_type        = decltype(std::declval<lambda_type>()(std::declval<first_value_type>()));
+        using second_future_type_ptr    = std::unique_ptr<second_future_type>;
+        using value_type                = typename second_future_type::value_type;
+        using this_type                 = and_then_future<value_type, lambda_type>;
+        using base_future_type          = base_future<value_type, this_type>;
+        using result_type               = typename base_future_type::result_type;
+
+    private:
+        lambda_type             _lambda;
+        first_future_type       _first;
+        second_future_type_ptr  _second;
+
+    public:
+        /**
+         * @brief Constructor.
+         */
+        template<
+            typename X_future,
+            typename X_lambda>
+        inline and_then_future(
             X_future&& p_first,
             X_lambda&& p_lambda)
-        : _first (std::forward<X_future>(p_first))
-        , _lambda(std::forward<X_lambda>(p_lambda))
-        { }
-
-    template<
-        typename T_future,
-        typename T_lambda>
-    typename and_then_future<T_future, T_lambda>::result_type
-    and_then_future<T_future, T_lambda>
-        ::poll()
-    {
-        while (true)
+            : _first (std::forward<X_future>(p_first))
+            , _lambda(std::forward<X_lambda>(p_lambda))
+            { }
+
+        inline and_then_future(and_then_future &&) = default;
+        inline and_then_future(and_then_future const &) = default;
+
+    public: /* future */
+        /**
+         * @brief Poll the result from the future.
+         */
+        inline result_type poll()
         {
-            if (_second)
-            {
-                return _second->poll();
-            }
-            else
+            while (true)
             {
-                auto r = _first.poll();
-                if (!r)
-                    return result_type::not_ready();
-
-                _second = std::make_unique<second_future_type>(r.call(_lambda));
+                if (_second)
+                {
+                    return _second->poll();
+                }
+                else
+                {
+                    auto r = _first.poll();
+                    if (!r)
+                        return result_type::not_ready();
+
+                    _second = std::make_unique<second_future_type>(r.call(_lambda));
+                }
             }
         }
-    }
+    };
 
     /* and_then_impl */
 
@@ -65,10 +92,6 @@ namespace __future {
         using derived_forward_type  = forward_type_t<X_mode, derived_ref_type>;
         using and_then_future_type  = __future::and_then_future<derived_storage_type, lambda_type>;
 
-        static_assert(
-            X_mode != ref || !std::is_rvalue_reference_v<self_type>,
-            "Can not store rvalue reference as lvalue reference!");
-
         auto& self = static_cast<derived_ref_type>(p_self);
 
         return and_then_future_type(
@@ -91,7 +114,9 @@ namespace asyncpp
         typename X_lambda>
     auto base_future<T_value, T_derived>
         ::and_then(X_lambda&& p_lambda) &
-        { return __future::and_then_impl<X_mode>(*this, std::forward<X_lambda>(p_lambda)); }
+    {
+        return __future::and_then_impl<X_mode>(*this, std::forward<X_lambda>(p_lambda));
+    }
 
     template<
         typename T_value,
@@ -101,6 +126,12 @@ namespace asyncpp
         typename X_lambda>
     auto base_future<T_value, T_derived>
         ::and_then(X_lambda&& p_lambda) &&
-        { return __future::and_then_impl<X_mode>(std::move(*this), std::forward<X_lambda>(p_lambda)); }
+    {
+        static_assert(
+            X_mode != ref,
+            "Can not store rvalue reference as lvalue reference!");
+
+        return __future::and_then_impl<X_mode>(std::move(*this), std::forward<X_lambda>(p_lambda));
+    }
 
 }
diff --git a/include/asyncpp/core/future/future.h b/include/asyncpp/core/future/future.h
new file mode 100644
index 0000000..2862d39
--- /dev/null
+++ b/include/asyncpp/core/future/future.h
@@ -0,0 +1,92 @@
+#pragma once
+
+#include <type_traits>
+
+#include "future.pre.h"
+#include "../misc.h"
+#include "../result.h"
+
+namespace asyncpp
+{
+
+    template<
+        typename T_value,
+        typename T_derived>
+    struct base_future
+        : public tag_future
+    {
+    public:
+        using value_type    = T_value;
+        using result_type   = future_result<value_type>;
+        using derived_type  = T_derived;
+        using this_type     = base_future<value_type, derived_type>;
+
+    public:
+        /**
+         * @brief Transform the result of this future.
+         */
+        template<
+            chaining_mode X_mode = copy,
+            typename X_lambda>
+        inline auto map(X_lambda&& p_lambda) &;
+
+        /**
+         * @brief Transform the result of this future.
+         */
+        template<
+            chaining_mode X_mode = move,
+            typename X_lambda>
+        inline auto map(X_lambda&& p_lambda) &&;
+
+    public:
+        /**
+         * @brief Execute the given lambda after the future is finished and
+         *        wait for the future returned by the lambda.
+         */
+        template<
+            chaining_mode X_mode = copy,
+            typename X_lambda>
+        inline auto and_then(X_lambda&& p_lambda) &;
+
+        /**
+         * @brief Execute the given lambda after the future is finished and
+         *        wait for the future returned by the lambda.
+         */
+        template<
+            chaining_mode X_mode = move,
+            typename X_lambda>
+        inline auto and_then(X_lambda&& p_lambda) &&;
+
+    #ifdef asyncpp_timing
+    public:
+        /**
+         * @brief Throw an execption if the timeout has passed.
+         *
+         * This method is only enabled if timer.h is included before.
+         */
+        template<
+            chaining_mode X_mode = copy,
+            typename X_base,
+            typename X_ratio>
+        inline auto timeout(const duration<X_base, X_ratio>& p_timeout) &;
+
+        /**
+         * @brief Throw an execption if the timeout has passed.
+         *
+         * This method is only enabled if timer.h is included before.
+         */
+        template<
+            chaining_mode X_mode = move,
+            typename X_base,
+            typename X_ratio>
+        inline auto timeout(const duration<X_base, X_ratio>& p_timeout) &&;
+    #endif
+    };
+
+    /**
+     * @brief Create a lazy evaluated future.
+     */
+    template<typename X_lambda>
+    inline auto lazy(X_lambda&& p_lambda);
+
+}
diff --git a/include/asyncpp/core/future.pre.h b/include/asyncpp/core/future/future.pre.h
similarity index 95%
rename from include/asyncpp/core/future.pre.h
rename to include/asyncpp/core/future/future.pre.h
index 8902d35..d1a992d 100644
--- a/include/asyncpp/core/future.pre.h
+++ b/include/asyncpp/core/future/future.pre.h
@@ -1,7 +1,5 @@
 #pragma once
 
-#include "misc.h"
-
 namespace asyncpp
 {
 
diff --git a/include/asyncpp/core/future/lazy.h b/include/asyncpp/core/future/lazy.h
deleted file mode 100644
index ca50eab..0000000
--- a/include/asyncpp/core/future/lazy.h
+++ /dev/null
@@ -1,67 +0,0 @@
-#pragma once
-
-#include "../future.pre.h"
-
-namespace asyncpp
-{
-
-    namespace __future
-    {
-
-        template<typename T_lambda>
-        struct lazy_future final :
-            public base_future<
-                decltype(std::declval<T_lambda>()()),
-                lazy_future<T_lambda>
-            >
-        {
-        public:
-            using lambda_type       = T_lambda;
-            using value_type        = decltype(std::declval<lambda_type>()());
-            using this_type         = lazy_future<lambda_type>;
-            using base_future_type  = base_future<value_type, this_type>;
-            using result_type       = typename base_future_type::result_type;
-
-        private:
-            lambda_type _lambda;
-
-        public:
-            /**
-             * @brief Constructor.
-             */
-            template<typename X_lambda>
-            inline lazy_future(
-                X_lambda&& p_lambda);
-
-            inline lazy_future(lazy_future &&) = default;
-            inline lazy_future(lazy_future const &) = default;
-
-        public: /* future */
-            /**
-             * @brief Poll the result from the future.
-             */
-            template<typename X = value_type>
-            inline auto poll()
-                -> std::enable_if_t<
-                    std::is_void_v<X>,
-                    result_type>;
-
-            /**
-             * @brief Poll the result from the future.
-             */
-            template<typename X = value_type>
-            inline auto poll()
-                -> std::enable_if_t<
-                    !std::is_void_v<X>,
-                    result_type>;
-        };
-
-    }
-
-    /**
-     * @brief Create a lazy evaluated future.
-     */
-    template<typename X_lambda>
-    inline auto lazy(X_lambda&& p_lambda);
-
-}
diff --git a/include/asyncpp/core/future/lazy.inl b/include/asyncpp/core/future/lazy.inl
index 4747e67..8d984b5 100644
--- a/include/asyncpp/core/future/lazy.inl
+++ b/include/asyncpp/core/future/lazy.inl
@@ -1,45 +1,71 @@
 #pragma once
 
-#include "lazy.h"
+#include "future.h"
 
-namespace asyncpp
-{
+namespace asyncpp {
+namespace __future {
 
-    namespace __future
+    template<typename T_lambda>
+    struct lazy_future final :
+        public base_future<
+            decltype(std::declval<T_lambda>()()),
+            lazy_future<T_lambda>
+        >
     {
+    public:
+        using lambda_type       = T_lambda;
+        using value_type        = decltype(std::declval<lambda_type>()());
+        using this_type         = lazy_future<lambda_type>;
+        using base_future_type  = base_future<value_type, this_type>;
+        using result_type       = typename base_future_type::result_type;
 
-        /* lazy_future */
+    private:
+        lambda_type _lambda;
 
-        template<typename T_lambda>
+    public:
+        /**
+         * @brief Constructor.
+         */
         template<typename X_lambda>
-        lazy_future<T_lambda>::lazy_future(
+        inline lazy_future(
             X_lambda&& p_lambda)
             : _lambda(std::forward<X_lambda>(p_lambda))
             { }
 
-        template<typename T_lambda>
-        template<typename X>
-        inline auto lazy_future<T_lambda>
-            ::poll()
-                -> std::enable_if_t<
-                    std::is_void_v<X>,
-                    result_type>
+        inline lazy_future(lazy_future &&) = default;
+        inline lazy_future(lazy_future const &) = default;
+
+    public: /* future */
+        /**
+         * @brief Poll the result from the future.
+         */
+        template<typename X = value_type>
+        inline auto poll()
+            -> std::enable_if_t<
+                std::is_void_v<X>,
+                result_type>
         {
             _lambda();
             return result_type::ready();
         }
 
-        template<typename T_lambda>
-        template<typename X>
-        inline auto lazy_future<T_lambda>
-            ::poll()
-                -> std::enable_if_t<
-                    !std::is_void_v<X>,
-                    result_type>
+        /**
+         * @brief Poll the result from the future.
+         */
+        template<typename X = value_type>
+        inline auto poll()
+            -> std::enable_if_t<
+                !std::is_void_v<X>,
+                result_type>
         {
             return result_type::ready(_lambda());
         }
-    }
+    };
+
+} }
+
+namespace asyncpp
+{
 
     template<typename X_lambda>
     inline auto lazy(X_lambda&& p_lambda)
diff --git a/include/asyncpp/core/future/map.h b/include/asyncpp/core/future/map.h
deleted file mode 100644
index 9a72f97..0000000
--- a/include/asyncpp/core/future/map.h
+++ /dev/null
@@ -1,51 +0,0 @@
-#pragma once
-
-#include "../future.pre.h"
-
-namespace asyncpp {
-namespace __future {
-
-    template<
-        typename T_future,
-        typename T_lambda>
-    struct map_future final :
-        public base_future<
-            typename std::decay_t<T_future>::value_type,
-            map_future<T_future, T_lambda>
-        >
-    {
-    public:
-        using future_type       = T_future;
-        using lambda_type       = T_lambda;
-        using future_value_type = typename std::decay_t<future_type>::value_type;
-        using value_type        = decltype(std::declval<lambda_type>()(std::declval<future_value_type>()));
-        using this_type         = map_future<future_type, lambda_type>;
-        using base_future_type  = base_future<value_type, this_type>;
-        using result_type       = typename base_future_type::result_type;
-
-    private:
-        future_type _future;
-        lambda_type _lambda;
-
-    public:
-        /**
-         * @brief Constructor.
-         */
-        template<
-            typename X_future,
-            typename X_lambda>
-        inline map_future(
-            X_future&& p_future,
-            X_lambda&& p_lambda);
-
-        inline map_future(map_future &&) = default;
-        inline map_future(map_future const &) = default;
-
-    public: /* future */
-        /**
-         * @brief Poll the result from the future.
-         */
-        inline result_type poll();
-    };
-
-} }
diff --git a/include/asyncpp/core/future/map.inl b/include/asyncpp/core/future/map.inl
index 9e67dd0..78b372f 100644
--- a/include/asyncpp/core/future/map.inl
+++ b/include/asyncpp/core/future/map.inl
@@ -1,38 +1,61 @@
 #pragma once
 
-#include "map.h"
+#include "future.h"
 
 namespace asyncpp {
 namespace __future {
 
-    /* map_future */
-
     template<
         typename T_future,
         typename T_lambda>
-    template<
-        typename X_future,
-        typename X_lambda>
-    map_future<T_future, T_lambda>
-        ::map_future(
+    struct map_future final :
+        public base_future<
+            typename std::decay_t<T_future>::value_type,
+            map_future<T_future, T_lambda>
+        >
+    {
+    public:
+        using future_type       = T_future;
+        using lambda_type       = T_lambda;
+        using future_value_type = typename std::decay_t<future_type>::value_type;
+        using value_type        = decltype(std::declval<lambda_type>()(std::declval<future_value_type>()));
+        using this_type         = map_future<future_type, lambda_type>;
+        using base_future_type  = base_future<value_type, this_type>;
+        using result_type       = typename base_future_type::result_type;
+
+    private:
+        future_type _future;
+        lambda_type _lambda;
+
+    public:
+        /**
+         * @brief Constructor.
+         */
+        template<
+            typename X_future,
+            typename X_lambda>
+        inline map_future(
             X_future&& p_future,
             X_lambda&& p_lambda)
-        : _future(std::forward<X_future>(p_future))
-        , _lambda(std::forward<X_lambda>(p_lambda))
-        { }
-
-    template<
-        typename T_future,
-        typename T_lambda>
-    typename map_future<T_future, T_lambda>::result_type
-    map_future<T_future, T_lambda>
-        ::poll()
-    {
-        auto r = _future.poll();
-        return r
-            ? result_type::ready(r.call(_lambda))
-            : result_type::not_ready();
-    }
+            : _future(std::forward<X_future>(p_future))
+            , _lambda(std::forward<X_lambda>(p_lambda))
+            { }
+
+        inline map_future(map_future &&) = default;
+        inline map_future(map_future const &) = default;
+
+    public: /* future */
+        /**
+         * @brief Poll the result from the future.
+         */
+        inline result_type poll()
+        {
+            auto r = _future.poll();
+            return r
+                ? result_type::ready(r.call(_lambda))
+                : result_type::not_ready();
+        }
+    };
 
     /* map_impl */
 
@@ -53,10 +76,6 @@ namespace __future {
         using derived_forward_type  = forward_type_t<X_mode, derived_ref_type>;
         using map_future_type       = __future::map_future<derived_storage_type, lambda_type>;
 
-        static_assert(
-            X_mode != ref || !std::is_rvalue_reference_v<self_type>,
-            "Can not store rvalue reference as lvalue reference!");
-
         auto& self = static_cast<derived_ref_type>(p_self);
 
         return map_future_type(
@@ -79,7 +98,9 @@ namespace asyncpp
         typename X_lambda>
     auto base_future<T_value, T_derived>
         ::map(X_lambda&& p_lambda) &
-        { return __future::map_impl<X_mode>(*this, std::forward<X_lambda>(p_lambda)); }
+    {
+        return __future::map_impl<X_mode>(*this, std::forward<X_lambda>(p_lambda));
+    }
 
     template<
         typename T_value,
@@ -89,6 +110,12 @@ namespace asyncpp
         typename X_lambda>
     auto base_future<T_value, T_derived>
         ::map(X_lambda&& p_lambda) &&
-        { return __future::map_impl<X_mode>(std::move(*this), std::forward<X_lambda>(p_lambda)); }
+    {
+        static_assert(
+            X_mode != ref,
+            "Can not store rvalue reference as lvalue reference!");
+
+        return __future::map_impl<X_mode>(std::move(*this), std::forward<X_lambda>(p_lambda));
+    }
 
 }
diff --git a/include/asyncpp/core/future/timeout.inl b/include/asyncpp/core/future/timeout.inl
index b324da5..d9a72ad 100644
--- a/include/asyncpp/core/future/timeout.inl
+++ b/include/asyncpp/core/future/timeout.inl
@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../future.h"
+#include "future.h"
 
 namespace asyncpp {
 namespace __future {
@@ -10,7 +10,7 @@ namespace __future {
         typename X_self,
         typename X_base,
         typename X_ratio>
-    auto helper_timeout(
+    auto timeout_impl(
         X_self&&                            p_self,
         const duration<X_base, X_ratio>&    p_timeout)
     {
@@ -22,7 +22,7 @@ namespace __future {
                                         derived_type const &,
                                         derived_type &>;
         using derived_forward_type  = forward_type_t<X_mode, derived_ref_type>;
-        using timeout_type   = timing::timeout<derived_storage_type>;
+        using timeout_type          = asyncpp::timing::timeout<derived_storage_type>;
 
         auto& self = static_cast<derived_ref_type>(p_self);
 
@@ -47,7 +47,9 @@ namespace asyncpp
         typename X_ratio>
     auto base_future<T_value, T_derived>
         ::timeout(const duration<X_base, X_ratio>& p_timeout) &
-        { return __future::helper_timeout<X_mode>(*this, p_timeout); }
+    {
+        return __future::timeout_impl<X_mode>(*this, p_timeout);
+    }
 
     template<
         typename T_value,
@@ -58,6 +60,12 @@ namespace asyncpp
         typename X_ratio>
     auto base_future<T_value, T_derived>
         ::timeout(const duration<X_base, X_ratio>& p_timeout) &&
-        { return __future::helper_timeout<X_mode>(std::move(*this), p_timeout); }
+    {
+        static_assert(
+            X_mode != ref,
+            "Can not store rvalue reference as lvalue reference!");
+
+        return __future::timeout_impl<X_mode>(std::move(*this), p_timeout);
+    }
 
 }
diff --git a/include/asyncpp/core/result.h b/include/asyncpp/core/result.h
index 330aec2..bae1570 100644
--- a/include/asyncpp/core/result.h
+++ b/include/asyncpp/core/result.h
@@ -1,139 +1,5 @@
 #pragma once
 
-#include <variant>
+#include "result/result.h"
 
-#include "result.pre.h"
-
-namespace asyncpp
-{
-
-    namespace __impl
-    {
-
-        struct result_not_ready
-            { };
-
-        struct result_done
-            { };
-
-        template<typename T_value>
-        struct result_ready
-        {
-            using value_type = T_value;
-
-            value_type value;
-
-            template<typename... T_args>
-            inline result_ready(T_args&&... p_args);
-        };
-
-        template<bool for_stream, typename T_value>
-        struct result
-        {
-        public:
-            using value_type            = T_value;
-            using not_ready_type        = result_not_ready;
-            using ready_type            = result_ready<value_type>;
-            using done_type             = result_done;
-            using storage_type          = std::conditional_t<
-                                            for_stream,
-                                            std::variant<not_ready_type, ready_type, done_type>,
-                                            std::variant<not_ready_type, ready_type>>;
-            using clean_value_type      = std::remove_reference_t<value_type>;
-            using pointer_type          = clean_value_type*;
-            using reference_type        = clean_value_type&;
-            using const_pointer_type    = clean_value_type const *;
-            using const_reference_type  = clean_value_type const &;
-
-        private:
-            storage_type _storage; //!< Stores the actual result.
-
-        private:
-            /**
-             * @brief Constructor.
-             */
-            inline result(storage_type&& p_storage);
-
-        public:
-            /**
-             * @brief returns a result that is not ready.
-             */
-            static inline auto& not_ready();
-
-            /**
-             * @brief returns a result that is not ready.
-             */
-            template<typename... X_args>
-            static inline auto ready(X_args&&... p_args);
-
-            /**
-             * @brief returns a result that is not ready.
-             */
-            template<
-                bool X = for_stream,
-                typename = std::enable_if_t<X>>
-            static inline auto& done();
-
-        public:
-            /**
-             * @brief Get the status of the result.
-             */
-            template<
-                bool X = for_stream,
-                typename = std::enable_if_t<X>>
-            inline result_status status() const;
-
-            /**
-             * @brief Check if the result is not ready (is pending).
-             */
-            inline bool is_not_ready() const;
-
-            /**
-             * @brief Check if the result is ready (has a value).
-             */
-            inline bool is_ready() const;
-
-            /**
-             * @brief Check if the result is done (stream is finished).
-             */
-            template<
-                bool X = for_stream,
-                typename = std::enable_if_t<X>>
-            inline bool is_done() const;
-
-            /**
-             * @brief Get the value of the result.
-             */
-            inline reference_type value();
-
-            /**
-             * @brief Get the value of the result.
-             */
-            inline const_reference_type value() const;
-
-            /**
-             * @brief Call the passed closure with the value stored in the result.
-             */
-            template<typename X_lambda>
-            inline auto call(const X_lambda& p_lambda);
-
-            /**
-             * @brief Call the passed closure with the value stored in the result.
-             */
-            template<typename X_lambda>
-            inline auto call(const X_lambda& p_lambda) const;
-
-        public:
-            inline operator bool() const;
-            inline pointer_type operator-> ();
-            inline reference_type operator* ();
-            inline const_pointer_type operator-> () const;
-            inline const_reference_type operator* () const;
-        };
-
-        template<bool for_stream>
-        struct result<for_stream, void>;
-
-    }
-
-}
+#include "result/result.inl"
diff --git a/include/asyncpp/core/result/result.h b/include/asyncpp/core/result/result.h
new file mode 100644
index 0000000..330aec2
--- /dev/null
+++ b/include/asyncpp/core/result/result.h
@@ -0,0 +1,139 @@
+#pragma once
+
+#include <variant>
+
+#include "result.pre.h"
+
+namespace asyncpp
+{
+
+    namespace __impl
+    {
+
+        struct result_not_ready
+            { };
+
+        struct result_done
+            { };
+
+        template<typename T_value>
+        struct result_ready
+        {
+            using value_type = T_value;
+
+            value_type value;
+
+            template<typename... T_args>
+            inline result_ready(T_args&&... p_args);
+        };
+
+        template<bool for_stream, typename T_value>
+        struct result
+        {
+        public:
+            using value_type            = T_value;
+            using not_ready_type        = result_not_ready;
+            using ready_type            = result_ready<value_type>;
+            using done_type             = result_done;
+            using storage_type          = std::conditional_t<
+                                            for_stream,
+                                            std::variant<not_ready_type, ready_type, done_type>,
+                                            std::variant<not_ready_type, ready_type>>;
+            using clean_value_type      = std::remove_reference_t<value_type>;
+            using pointer_type          = clean_value_type*;
+            using reference_type        = clean_value_type&;
+            using const_pointer_type    = clean_value_type const *;
+            using const_reference_type  = clean_value_type const &;
+
+        private:
+            storage_type _storage; //!< Stores the actual result.
+
+        private:
+            /**
+             * @brief Constructor.
+             */
+            inline result(storage_type&& p_storage);
+
+        public:
+            /**
+             * @brief returns a result that is not ready.
+             */
+            static inline auto& not_ready();
+
+            /**
+             * @brief returns a result that is not ready.
+             */
+            template<typename... X_args>
+            static inline auto ready(X_args&&... p_args);
+
+            /**
+             * @brief returns a result that is not ready.
+             */
+            template<
+                bool X = for_stream,
+                typename = std::enable_if_t<X>>
+            static inline auto& done();
+
+        public:
+            /**
+             * @brief Get the status of the result.
+             */
+            template<
+                bool X = for_stream,
+                typename = std::enable_if_t<X>>
+            inline result_status status() const;
+
+            /**
+             * @brief Check if the result is not ready (is pending).
+             */
+            inline bool is_not_ready() const;
+
+            /**
+             * @brief Check if the result is ready (has a value).
+             */
+            inline bool is_ready() const;
+
+            /**
+             * @brief Check if the result is done (stream is finished).
+             */
+            template<
+                bool X = for_stream,
+                typename = std::enable_if_t<X>>
+            inline bool is_done() const;
+
+            /**
+             * @brief Get the value of the result.
+             */
+            inline reference_type value();
+
+            /**
+             * @brief Get the value of the result.
+             */
+            inline const_reference_type value() const;
+
+            /**
+             * @brief Call the passed closure with the value stored in the result.
+             */
+            template<typename X_lambda>
+            inline auto call(const X_lambda& p_lambda);
+
+            /**
+             * @brief Call the passed closure with the value stored in the result.
+             */
+            template<typename X_lambda>
+            inline auto call(const X_lambda& p_lambda) const;
+
+        public:
+            inline operator bool() const;
+            inline pointer_type operator-> ();
+            inline reference_type operator* ();
+            inline const_pointer_type operator-> () const;
+            inline const_reference_type operator* () const;
+        };
+
+        template<bool for_stream>
+        struct result<for_stream, void>;
+
+    }
+
+}
diff --git a/include/asyncpp/core/result.inl b/include/asyncpp/core/result/result.inl
similarity index 100%
rename from include/asyncpp/core/result.inl
rename to include/asyncpp/core/result/result.inl
diff --git a/include/asyncpp/core/result.pre.h b/include/asyncpp/core/result/result.pre.h
similarity index 100%
rename from include/asyncpp/core/result.pre.h
rename to include/asyncpp/core/result/result.pre.h
diff --git a/include/asyncpp/core/stream.h b/include/asyncpp/core/stream.h
index 8271f14..f70b0c4 100644
--- a/include/asyncpp/core/stream.h
+++ b/include/asyncpp/core/stream.h
@@ -1,114 +1,11 @@
 #pragma once
 
-#include <type_traits>
+#include "stream/stream.h"
 
-#include "result.h"
-#include "stream.pre.h"
+#include "stream/map.inl"
+#include "stream/flatten.inl"
+#include "stream/for_each.inl"
 
-namespace asyncpp
-{
-
-    template<
-        typename T_value,
-        typename T_derived>
-    struct base_stream
-        : public tag_stream
-    {
-    public:
-        using value_type    = T_value;
-        using result_type   = stream_result<value_type>;
-        using derived_type  = T_derived;
-        using this_type     = base_stream<value_type, derived_type>;
-
-    public:
-        /**
-         * @brief Execute the given lambda for each element in the stream.
-         *
-         * @return Returns a future that completes once the stream is finished.
-         */
-        template<typename X_lambda>
-        inline auto for_each(X_lambda&& p_lambda) const &;
-
-        /**
-         * @brief Execute the given lambda for each element in the stream.
-         *
-         * @return Returns a future that completes once the stream is finished.
-         */
-        template<typename X_lambda>
-        inline auto for_each(X_lambda&& p_lambda) &;
-
-        /**
-         * @brief Execute the given lambda for each element in the stream.
-         *
-         * @return Returns a future that completes once the stream is finished.
-         */
-        template<typename X_lambda>
-        inline auto for_each(X_lambda&& p_lambda) &&;
-
-    public:
-        /**
-         * @brief Transforms the stream from one type to another type
-         *        by executing the passed lambda for each value.
-         */
-        template<typename X_lambda>
-        inline auto map(X_lambda&& p_lambda) const &;
-
-        /**
-         * @brief Transforms the stream from one type to another type
-         *        by executing the passed lambda for each value.
-         */
-        template<typename X_lambda>
-        inline auto map(X_lambda&& p_lambda) &;
-
-        /**
-         * @brief Transforms the stream from one type to another type
-         *        by executing the passed lambda for each value.
-         */
-        template<typename X_lambda>
-        inline auto map(X_lambda&& p_lambda) &&;
-
-    public:
-        /**
-         * @brief Flatten the stream of streams to a single stream.
-         */
-        inline auto flatten() const &;
-
-        /**
-         * @brief Flatten the stream of streams to a single stream.
-         */
-        inline auto flatten() &;
-
-        /**
-         * @brief Flatten the stream of streams to a single stream.
-         */
-        inline auto flatten() &&;
-
-    #ifdef asyncpp_timing
-    public:
-        /**
-         * @brief Throw an execption if the timeout has passed.
-         *
-         * This method is only enabled if timer.h is included before.
-         */
-        template<typename X_base, typename X_ratio>
-        inline auto timeout(const duration<X_base, X_ratio>& p_timeout) const &;
-
-        /**
-         * @brief Throw an execption if the timeout has passed.
-         *
-         * This method is only enabled if timer.h is included before.
-         */
-        template<typename X_base, typename X_ratio>
-        inline auto timeout(const duration<X_base, X_ratio>& p_timeout) &;
-
-        /**
-         * @brief Throw an execption if the timeout has passed.
-         *
-         * This method is only enabled if timer.h is included before.
-         */
-        template<typename X_base, typename X_ratio>
-        inline auto timeout(const duration<X_base, X_ratio>& p_timeout) &&;
-    #endif
-    };
-
-}
+#ifdef asyncpp_timing
+#include "stream/timeout.inl"
+#endif
diff --git a/include/asyncpp/core/stream.inl b/include/asyncpp/core/stream.inl
deleted file mode 100644
index 17996e9..0000000
--- a/include/asyncpp/core/stream.inl
+++ /dev/null
@@ -1,230 +0,0 @@
-#pragma once
-
-#include "stream.h"
-
-#include "stream/map.inl"
-#include "stream/flatten.inl"
-#include "stream/for_each.inl"
-
-#ifdef asyncpp_timing
-#include <asyncpp/timing/timeout.inl>
-#endif
-
-namespace asyncpp
-{
-
-    /* base_stream::for_each */
-
-    template<
-        typename T_value,
-        typename T_derived>
-    template<
-        typename X_lambda>
-    auto base_stream<T_value, T_derived>
-        ::for_each(X_lambda&& p_lambda) const &
-    {
-        using lambda_type   = X_lambda;
-        using for_each_type = __stream::for_each_impl<derived_type, lambda_type>;
-
-        auto& self = static_cast<derived_type const &>(*this);
-
-        return for_each_type(
-            std::forward<derived_type const>(self),
-            std::forward<X_lambda>(p_lambda));
-    }
-
-    template<
-        typename T_value,
-        typename T_derived>
-    template<
-        typename X_lambda>
-    auto base_stream<T_value, T_derived>
-        ::for_each(X_lambda&& p_lambda) &
-    {
-        using lambda_type   = X_lambda;
-        using for_each_type = __stream::for_each_impl<derived_type&, lambda_type>;
-
-        auto& self = static_cast<derived_type &>(*this);
-
-        return for_each_type(
-            std::forward<derived_type &>(self),
-            std::forward<X_lambda>(p_lambda));
-    }
-
-    template<
-        typename T_value,
-        typename T_derived>
-    template<
-        typename X_lambda>
-    auto base_stream<T_value, T_derived>
-        ::for_each(X_lambda&& p_lambda) &&
-    {
-        using lambda_type   = X_lambda;
-        using for_each_type = __stream::for_each_impl<derived_type, lambda_type>;
-
-        auto& self = static_cast<derived_type &>(*this);
-
-        return for_each_type(
-            std::forward<derived_type &&>(self),
-            std::forward<X_lambda>(p_lambda));
-    }
-
-    /* base_stream::map */
-
-    template<
-        typename T_value,
-        typename T_derived>
-    template<
-        typename X_lambda>
-    auto base_stream<T_value, T_derived>
-        ::map(X_lambda&& p_lambda) const &
-    {
-        using lambda_type = X_lambda;
-        using map_type    = __stream::map_future<derived_type, lambda_type>;
-
-        auto& self = static_cast<derived_type const &>(*this);
-
-        return map_type(
-            std::forward<derived_type const &>(self),
-            std::forward<X_lambda>(p_lambda));
-    }
-
-    template<
-        typename T_value,
-        typename T_derived>
-    template<
-        typename X_lambda>
-    auto base_stream<T_value, T_derived>
-        ::map(X_lambda&& p_lambda) &
-    {
-        using lambda_type = X_lambda;
-        using map_type    = __stream::map_future<derived_type, lambda_type>;
-
-        auto& self = static_cast<derived_type &>(*this);
-
-        return map_type(
-            std::forward<derived_type &>(self),
-            std::forward<X_lambda>(p_lambda));
-    }
-
-    template<
-        typename T_value,
-        typename T_derived>
-    template<
-        typename X_lambda>
-    auto base_stream<T_value, T_derived>
-        ::map(X_lambda&& p_lambda) &&
-    {
-        using lambda_type = X_lambda;
-        using map_type    = __stream::map_future<derived_type, lambda_type>;
-
-        auto& self = static_cast<derived_type &>(*this);
-
-        return map_type(
-            std::forward<derived_type &&>(self),
-            std::forward<X_lambda>(p_lambda));
-    }
-
-    /* base_stream::flatten */
-
-    template<
-        typename T_value,
-        typename T_derived>
-    auto base_stream<T_value, T_derived>
-        ::flatten() const &
-    {
-        using flatten_type = __stream::flatten_impl<derived_type>;
-
-        auto& self = static_cast<derived_type const &>(*this);
-
-        return flatten_type(
-            std::forward<derived_type const &>(self));
-    }
-
-    template<
-        typename T_value,
-        typename T_derived>
-    auto base_stream<T_value, T_derived>
-        ::flatten() &
-    {
-        using flatten_type = __stream::flatten_impl<derived_type>;
-
-        auto& self = static_cast<derived_type &>(*this);
-
-        return flatten_type(
-            std::forward<derived_type &>(self));
-    }
-
-    template<
-        typename T_value,
-        typename T_derived>
-    auto base_stream<T_value, T_derived>
-        ::flatten() &&
-    {
-        using flatten_type = __stream::flatten_impl<derived_type>;
-
-        auto& self = static_cast<derived_type &>(*this);
-
-        return flatten_type(
-            std::forward<derived_type &&>(self));
-    }
-
-    /* base_stream::timeout */
-
-    #ifdef asyncpp_timing
-    template<
-        typename T_value,
-        typename T_derived>
-    template<
-        typename X_base,
-        typename X_ratio>
-    auto base_stream<T_value, T_derived>
-        ::timeout(const duration<X_base, X_ratio>& p_timeout) const &
-    {
-        using timeout_type = timing::timeout<derived_type>;
-
-        auto& self = static_cast<derived_type const &>(*this);
-
-        return timeout_type(
-            std::forward<derived_type const>(self),
-            p_timeout);
-    }
-
-    template<
-        typename T_value,
-        typename T_derived>
-    template<
-        typename X_base,
-        typename X_ratio>
-    auto base_stream<T_value, T_derived>
-        ::timeout(const duration<X_base, X_ratio>& p_timeout) &
-    {
-        using timeout_type = timing::timeout<derived_type&>;
-
-        auto& self = static_cast<derived_type &>(*this);
-
-        return timeout_type(
-            std::forward<derived_type &>(self),
-            p_timeout);
-    }
-
-    template<
-        typename T_value,
-        typename T_derived>
-    template<
-        typename X_base,
-        typename X_ratio>
-    auto base_stream<T_value, T_derived>
-        ::timeout(const duration<X_base, X_ratio>& p_timeout) &&
-    {
-        using timeout_type = timing::timeout<derived_type>;
-
-        auto& self = static_cast<derived_type &>(*this);
-
-        return timeout_type(
-            std::forward<derived_type &&>(self),
-            p_timeout);
-    }
-    #endif
-
-}
diff --git a/include/asyncpp/core/stream/flatten.h b/include/asyncpp/core/stream/flatten.h
deleted file mode 100644
index 9c61190..0000000
--- a/include/asyncpp/core/stream/flatten.h
+++ /dev/null
@@ -1,47 +0,0 @@
-#pragma once
-
-#include <memory>
-
-#include <asyncpp/core/stream.pre.h>
-
-namespace asyncpp {
-namespace __stream {
-
-    template<
-        typename T_stream>
-    struct flatten_impl final :
-        public base_stream<
-            typename T_stream::value_type::value_type,
-            flatten_impl<T_stream>
-        >
-    {
-    public:
-        using stream_type           = T_stream;
-        using inner_stream_type     = typename stream_type::value_type;
-        using inner_stream_ptr_u    = std::unique_ptr<inner_stream_type>;
-        using value_type            = typename inner_stream_type::value_type;
-        using this_type             = flatten_impl<stream_type>;
-        using base_stream_type      = base_stream<value_type, this_type>;
-        using result_type           = typename base_stream_type::result_type;
-
-    private:
-        stream_type         _stream;
-        inner_stream_ptr_u  _inner;
-
-    public:
-        /**
-         * @brief Constructor.
-         */
-        template<
-            typename X_stream>
-        inline flatten_impl(
-            X_stream&& p_stream);
-
-    public: /* future */
-        /**
-         * @brief Poll the result from the future.
-         */
-        inline result_type poll();
-    };
-
-} }
diff --git a/include/asyncpp/core/stream/flatten.inl b/include/asyncpp/core/stream/flatten.inl
index aa1b6d5..13eb428 100644
--- a/include/asyncpp/core/stream/flatten.inl
+++ b/include/asyncpp/core/stream/flatten.inl
@@ -1,49 +1,130 @@
 #pragma once
 
-#include "flatten.h"
+#include <memory>
+
+#include "stream.h"
 
 namespace asyncpp {
 namespace __stream {
 
-    /* flatten_impl */
-
     template<
         typename T_stream>
-    template<
-        typename X_stream>
-    flatten_impl<T_stream>::flatten_impl(
-        X_stream&& p_stream)
-        : _stream   (std::forward<X_stream>(p_stream))
-        , _inner    ()
-        { }
-
-    template<
-        typename T_stream>
-    typename flatten_impl<T_stream>::result_type
-    flatten_impl<T_stream>
-        ::poll()
+    struct flatten_stream final :
+        public base_stream<
+            typename T_stream::value_type::value_type,
+            flatten_stream<T_stream>
+        >
     {
-        while (true)
+    public:
+        using stream_type           = T_stream;
+        using inner_stream_type     = typename stream_type::value_type;
+        using inner_stream_ptr_u    = std::unique_ptr<inner_stream_type>;
+        using value_type            = typename inner_stream_type::value_type;
+        using this_type             = flatten_stream<stream_type>;
+        using base_stream_type      = base_stream<value_type, this_type>;
+        using result_type           = typename base_stream_type::result_type;
+
+    private:
+        stream_type         _stream;
+        inner_stream_ptr_u  _inner;
+
+    public:
+        /**
+         * @brief Constructor.
+         */
+        template<
+            typename X_stream>
+        inline flatten_stream(
+            X_stream&& p_stream)
+            : _stream   (std::forward<X_stream>(p_stream))
+            , _inner    ()
+            { }
+
+        inline flatten_stream(flatten_stream &&) = default;
+        inline flatten_stream(flatten_stream const &) = default;
+
+    public: /* future */
+        /**
+         * @brief Poll the result from the future.
+         */
+        inline result_type poll()
         {
-            if (_inner)
+            while (true)
             {
-                auto r = _inner->poll();
+                if (_inner)
+                {
+                    auto r = _inner->poll();
 
-                if (!r.is_done())
-                    return r;
+                    if (!r.is_done())
+                        return r;
 
-                _inner.reset();
-            }
+                    _inner.reset();
+                }
 
-            auto r = _stream.poll();
-            if (r.is_done())
-                return result_type::done();
+                auto r = _stream.poll();
+                if (r.is_done())
+                    return result_type::done();
 
-            if (r.is_not_ready())
-                return result_type::not_ready();
+                if (r.is_not_ready())
+                    return result_type::not_ready();
 
-            _inner = std::make_unique<inner_stream_type>(std::move(*r));
+                _inner = std::make_unique<inner_stream_type>(std::move(*r));
+            }
         }
+    };
+
+    /* flatten_impl */
+
+    template<
+        chaining_mode X_mode,
+        typename X_self>
+    auto map_impl(X_self&& p_self)
+    {
+        using self_type             = X_self;
+        using derived_type          = typename std::decay_t<self_type>::derived_type;
+        using derived_storage_type  = storage_type_t<X_mode, derived_type>;
+        using derived_ref_type      = std::conditional_t<
+                                        std::is_const_v<std::remove_reference_t<self_type>>,
+                                        derived_type const &,
+                                        derived_type &>;
+        using derived_forward_type  = forward_type_t<X_mode, derived_ref_type>;
+        using flatten_stream_type   = __stream::flatten_stream<derived_storage_type>;
+
+        auto& self = static_cast<derived_ref_type>(p_self);
+
+        return flatten_stream_type(
+            std::forward<derived_forward_type>(self));
     }
 
 } }
+
+namespace asyncpp
+{
+
+    template<
+        typename T_value,
+        typename T_derived>
+    template<
+        chaining_mode X_mode>
+    auto base_stream<T_value, T_derived>
+        ::flatten() &
+    {
+        return __stream::map_impl<X_mode>(*this);
+    }
+
+    template<
+        typename T_value,
+        typename T_derived>
+    template<
+        chaining_mode X_mode>
+    auto base_stream<T_value, T_derived>
+        ::flatten() &&
+    {
+        static_assert(
+            X_mode != ref,
+            "Can not store rvalue reference as lvalue reference!");
+
+        return __stream::map_impl<X_mode>(std::move(*this));
+    }
+
+}
diff --git a/include/asyncpp/core/stream/for_each.h b/include/asyncpp/core/stream/for_each.h
deleted file mode 100644
index d31265e..0000000
--- a/include/asyncpp/core/stream/for_each.h
+++ /dev/null
@@ -1,47 +0,0 @@
-#pragma once
-
-#include <asyncpp/core/future.pre.h>
-
-namespace asyncpp {
-namespace __stream {
-
-    template<
-        typename T_stream,
-        typename T_lambda>
-    struct for_each_impl final :
-        public base_future<
-            void,
-            for_each_impl<T_stream, T_lambda>
-        >
-    {
-    public:
-        using stream_type       = T_stream;
-        using lambda_type       = T_lambda;
-        using value_type        = void;
-        using this_type         = for_each_impl<stream_type, lambda_type>;
-        using base_future_type  = base_future<value_type, this_type>;
-        using result_type       = typename base_future_type::result_type;
-
-    private:
-        stream_type _stream;
-        lambda_type _lambda;
-
-    public:
-        /**
-         * @brief Constructor.
-         */
-        template<
-            typename X_stream,
-            typename X_lambda>
-        inline for_each_impl(
-            X_stream&& p_stream,
-            X_lambda&& p_lambda);
-
-    public: /* future */
-        /**
-         * @brief Poll the result from the future.
-         */
-        inline result_type poll();
-    };
-
-} }
diff --git a/include/asyncpp/core/stream/for_each.inl b/include/asyncpp/core/stream/for_each.inl
index d4e2900..21e23d1 100644
--- a/include/asyncpp/core/stream/for_each.inl
+++ b/include/asyncpp/core/stream/for_each.inl
@@ -1,44 +1,123 @@
 #pragma once
 
-#include "for_each.h"
+#include "stream.h"
 
 namespace asyncpp {
 namespace __stream {
 
-    /* for_each_impl */
-
     template<
         typename T_stream,
         typename T_lambda>
-    template<
-        typename X_stream,
-        typename X_lambda>
-    for_each_impl<T_stream, T_lambda>
-        ::for_each_impl(
+    struct for_each_future final :
+        public base_future<
+            void,
+            for_each_future<T_stream, T_lambda>
+        >
+    {
+    public:
+        using stream_type       = T_stream;
+        using lambda_type       = T_lambda;
+        using value_type        = void;
+        using this_type         = for_each_future<stream_type, lambda_type>;
+        using base_future_type  = base_future<value_type, this_type>;
+        using result_type       = typename base_future_type::result_type;
+
+    private:
+        stream_type _stream;
+        lambda_type _lambda;
+
+    public:
+        /**
+         * @brief Constructor.
+         */
+        template<
+            typename X_stream,
+            typename X_lambda>
+        inline for_each_future(
             X_stream&& p_stream,
             X_lambda&& p_lambda)
-        : _stream(std::forward<X_stream>(p_stream))
-        , _lambda(std::forward<X_lambda>(p_lambda))
-        { }
+            : _stream(std::forward<X_stream>(p_stream))
+            , _lambda(std::forward<X_lambda>(p_lambda))
+            { }
 
-    template<
-        typename T_stream,
-        typename T_lambda>
-    typename for_each_impl<T_stream, T_lambda>::result_type
-    for_each_impl<T_stream, T_lambda>
-        ::poll()
-    {
-        while (true)
+        inline for_each_future(for_each_future &&) = default;
+        inline for_each_future(for_each_future const &) = default;
+
+    public: /* future */
+        /**
+         * @brief Poll the result from the future.
+         */
+        inline result_type poll()
         {
-            auto r = _stream.poll();
-            if (r.is_done())
-                return result_type::ready();
+            while (true)
+            {
+                auto r = _stream.poll();
+                if (r.is_done())
+                    return result_type::ready();
 
-            if (r.is_not_ready())
-                return result_type::not_ready();
+                if (r.is_not_ready())
+                    return result_type::not_ready();
 
-            r.call(_lambda);
+                r.call(_lambda);
+            }
         }
+    };
+
+    template<
+        chaining_mode X_mode,
+        typename X_self,
+        typename X_lambda>
+    auto for_each_impl(X_self&& p_self, X_lambda&& p_lambda)
+    {
+        using self_type             = X_self;
+        using lambda_type           = X_lambda;
+        using derived_type          = typename std::decay_t<self_type>::derived_type;
+        using derived_storage_type  = storage_type_t<X_mode, derived_type>;
+        using derived_ref_type      = std::conditional_t<
+                                        std::is_const_v<std::remove_reference_t<self_type>>,
+                                        derived_type const &,
+                                        derived_type &>;
+        using derived_forward_type  = forward_type_t<X_mode, derived_ref_type>;
+        using for_each_future_type  = __stream::for_each_future<derived_storage_type, lambda_type>;
+
+        auto& self = static_cast<derived_ref_type>(p_self);
+
+        return for_each_future_type(
+            std::forward<derived_forward_type>(self),
+            std::forward<X_lambda>(p_lambda));
     }
 
 } }
+
+namespace asyncpp
+{
+
+    template<
+        typename T_value,
+        typename T_derived>
+    template<
+        chaining_mode X_mode,
+        typename X_lambda>
+    auto base_stream<T_value, T_derived>
+        ::for_each(X_lambda&& p_lambda) &
+    {
+        return __stream::for_each_impl<X_mode>(*this, std::forward<X_lambda>(p_lambda));
+    }
+
+    template<
+        typename T_value,
+        typename T_derived>
+    template<
+        chaining_mode X_mode,
+        typename X_lambda>
+    auto base_stream<T_value, T_derived>
+        ::for_each(X_lambda&& p_lambda) &&
+    {
+        static_assert(
+            X_mode != ref,
+            "Can not store rvalue reference as lvalue reference!");
+
+        return __stream::for_each_impl<X_mode>(std::move(*this), std::forward<X_lambda>(p_lambda));
+    }
+
+}
diff --git a/include/asyncpp/core/stream/map.h b/include/asyncpp/core/stream/map.h
deleted file mode 100644
index ab69f49..0000000
--- a/include/asyncpp/core/stream/map.h
+++ /dev/null
@@ -1,48 +0,0 @@
-#pragma once
-
-#include <asyncpp/core/stream.pre.h>
-
-namespace asyncpp {
-namespace __stream {
-
-    template<
-        typename T_stream,
-        typename T_lambda>
-    struct map_future final :
-        public base_stream<
-            decltype(std::declval<T_lambda>()(std::declval<typename T_stream::value_type>())),
-            map_future<T_stream, T_lambda>
-        >
-    {
-    public:
-        using stream_type       = T_stream;
-        using lambda_type       = T_lambda;
-        using inner_value_type  = typename stream_type::value_type;
-        using value_type        = decltype(std::declval<lambda_type>()(std::declval<inner_value_type>()));
-        using this_type         = map_future<stream_type, lambda_type>;
-        using base_stream_type  = base_stream<value_type, this_type>;
-        using result_type       = typename base_stream_type::result_type;
-
-    private:
-        stream_type _stream;
-        lambda_type _lambda;
-
-    public:
-        /**
-         * @brief Constructor.
-         */
-        template<
-            typename X_stream,
-            typename X_lambda>
-        inline map_future(
-            X_stream&& p_stream,
-            X_lambda&& p_lambda);
-
-    public: /* future */
-        /**
-         * @brief Poll the result from the future.
-         */
-        inline result_type poll();
-    };
-
-} }
diff --git a/include/asyncpp/core/stream/map.inl b/include/asyncpp/core/stream/map.inl
index c39e3c5..02f61b5 100644
--- a/include/asyncpp/core/stream/map.inl
+++ b/include/asyncpp/core/stream/map.inl
@@ -1,40 +1,121 @@
 #pragma once
 
-#include "map.h"
+#include "stream.h"
 
 namespace asyncpp {
 namespace __stream {
 
-    /* map_future */
-
     template<
         typename T_stream,
         typename T_lambda>
+    struct map_stream final :
+        public base_stream<
+            decltype(std::declval<T_lambda>()(std::declval<typename T_stream::value_type>())),
+            map_stream<T_stream, T_lambda>
+        >
+    {
+    public:
+        using stream_type       = T_stream;
+        using lambda_type       = T_lambda;
+        using inner_value_type  = typename stream_type::value_type;
+        using value_type        = decltype(std::declval<lambda_type>()(std::declval<inner_value_type>()));
+        using this_type         = map_stream<stream_type, lambda_type>;
+        using base_stream_type  = base_stream<value_type, this_type>;
+        using result_type       = typename base_stream_type::result_type;
+
+    private:
+        stream_type _stream;
+        lambda_type _lambda;
+
+    public:
+        /**
+         * @brief Constructor.
+         */
+        template<
+            typename X_stream,
+            typename X_lambda>
+        inline map_stream(
+            X_stream&& p_stream,
+            X_lambda&& p_lambda)
+            : _stream(std::forward<X_stream>(p_stream))
+            , _lambda(std::forward<X_lambda>(p_lambda))
+            { }
+
+        inline map_stream(map_stream &&) = default;
+        inline map_stream(map_stream const &) = default;
+
+    public: /* future */
+        /**
+         * @brief Poll the result from the future.
+         */
+        inline result_type poll()
+        {
+            auto r = _stream.poll();
+            if (r.is_done())
+                return result_type::done();
+
+            if (r.is_ready())
+                return result_type::ready(r.call(_lambda));
+
+            return result_type::not_ready();
+        }
+    };
+
     template<
-        typename X_stream,
+        chaining_mode X_mode,
+        typename X_self,
         typename X_lambda>
-    map_future<T_stream, T_lambda>::map_future(
-        X_stream&& p_stream,
-        X_lambda&& p_lambda)
-        : _stream(std::forward<X_stream>(p_stream))
-        , _lambda(std::forward<X_lambda>(p_lambda))
-        { }
+    auto map_impl(X_self&& p_self, X_lambda&& p_lambda)
+    {
+        using self_type             = X_self;
+        using lambda_type           = X_lambda;
+        using derived_type          = typename std::decay_t<self_type>::derived_type;
+        using derived_storage_type  = storage_type_t<X_mode, derived_type>;
+        using derived_ref_type      = std::conditional_t<
+                                        std::is_const_v<std::remove_reference_t<self_type>>,
+                                        derived_type const &,
+                                        derived_type &>;
+        using derived_forward_type  = forward_type_t<X_mode, derived_ref_type>;
+        using map_stream_type       = __stream::map_stream<derived_storage_type, lambda_type>;
+
+        auto& self = static_cast<derived_ref_type>(p_self);
+
+        return map_stream_type(
+            std::forward<derived_forward_type>(self),
+            std::forward<X_lambda>(p_lambda));
+    }
+
+} }
+
+namespace asyncpp
+{
 
     template<
-        typename T_stream,
-        typename T_lambda>
-    typename map_future<T_stream, T_lambda>::result_type
-    map_future<T_stream, T_lambda>
-        ::poll()
+        typename T_value,
+        typename T_derived>
+    template<
+        chaining_mode X_mode,
+        typename X_lambda>
+    auto base_stream<T_value, T_derived>
+        ::map(X_lambda&& p_lambda) &
     {
-        auto r = _stream.poll();
-        if (r.is_done())
-            return result_type::done();
+        return __stream::map_impl<X_mode>(*this, std::forward<X_lambda>(p_lambda));
+    }
 
-        if (r.is_ready())
-            return result_type::ready(r.call(_lambda));
+    template<
+        typename T_value,
+        typename T_derived>
+    template<
+        chaining_mode X_mode,
+        typename X_lambda>
+    auto base_stream<T_value, T_derived>
+        ::map(X_lambda&& p_lambda) &&
+    {
+        static_assert(
+            X_mode != ref,
+            "Can not store rvalue reference as lvalue reference!");
 
-        return result_type::not_ready();
+        return __stream::map_impl<X_mode>(std::move(*this), std::forward<X_lambda>(p_lambda));
     }
 
-} }
+}
diff --git a/include/asyncpp/core/stream/stream.h b/include/asyncpp/core/stream/stream.h
new file mode 100644
index 0000000..038e98d
--- /dev/null
+++ b/include/asyncpp/core/stream/stream.h
@@ -0,0 +1,104 @@
+#pragma once
+
+#include <type_traits>
+
+#include "stream.pre.h"
+#include "../result.h"
+
+namespace asyncpp
+{
+
+    template<
+        typename T_value,
+        typename T_derived>
+    struct base_stream
+        : public tag_stream
+    {
+    public:
+        using value_type    = T_value;
+        using result_type   = stream_result<value_type>;
+        using derived_type  = T_derived;
+        using this_type     = base_stream<value_type, derived_type>;
+
+    public:
+        /**
+         * @brief Execute the given lambda for each element in the stream.
+         *
+         * @return Returns a future that completes once the stream is finished.
+         */
+        template<
+            chaining_mode X_mode = copy,
+            typename X_lambda>
+        inline auto for_each(X_lambda&& p_lambda) &;
+
+        /**
+         * @brief Execute the given lambda for each element in the stream.
+         *
+         * @return Returns a future that completes once the stream is finished.
+         */
+        template<
+            chaining_mode X_mode = move,
+            typename X_lambda>
+        inline auto for_each(X_lambda&& p_lambda) &&;
+
+    public:
+        /**
+         * @brief Transforms the stream from one type to another type
+         *        by executing the passed lambda for each value.
+         */
+        template<
+            chaining_mode X_mode = copy,
+            typename X_lambda>
+        inline auto map(X_lambda&& p_lambda) &;
+
+        /**
+         * @brief Transforms the stream from one type to another type
+         *        by executing the passed lambda for each value.
+         */
+        template<
+            chaining_mode X_mode = move,
+            typename X_lambda>
+        inline auto map(X_lambda&& p_lambda) &&;
+
+    public:
+        /**
+         * @brief Flatten the stream of streams to a single stream.
+         */
+        template<
+            chaining_mode X_mode = copy>
+        inline auto flatten() &;
+
+        /**
+         * @brief Flatten the stream of streams to a single stream.
+         */
+        template<
+            chaining_mode X_mode = move>
+        inline auto flatten() &&;
+
+    #ifdef asyncpp_timing
+    public:
+        /**
+         * @brief Throw an execption if the timeout has passed.
+         *
+         * This method is only enabled if timer.h is included before.
+         */
+        template<
+            chaining_mode X_mode = copy,
+            typename X_base,
+            typename X_ratio>
+        inline auto timeout(const duration<X_base, X_ratio>& p_timeout) &;
+
+        /**
+         * @brief Throw an execption if the timeout has passed.
+         *
+         * This method is only enabled if timer.h is included before.
+         */
+        template<
+            chaining_mode X_mode = move,
+            typename X_base,
+            typename X_ratio>
+        inline auto timeout(const duration<X_base, X_ratio>& p_timeout) &&;
+    #endif
+    };
+
+}
diff --git a/include/asyncpp/core/stream.pre.h b/include/asyncpp/core/stream/stream.pre.h
similarity index 100%
rename from include/asyncpp/core/stream.pre.h
rename to include/asyncpp/core/stream/stream.pre.h
diff --git a/include/asyncpp/core/stream/timeout.inl b/include/asyncpp/core/stream/timeout.inl
new file mode 100644
index 0000000..8b9159f
--- /dev/null
+++ b/include/asyncpp/core/stream/timeout.inl
@@ -0,0 +1,69 @@
+#pragma once
+
+#include "stream.h"
+
+namespace asyncpp {
+namespace __stream {
+
+     template<
+        chaining_mode X_mode,
+        typename X_self,
+        typename X_base,
+        typename X_ratio>
+    auto timeout_impl(
+        X_self&&                            p_self,
+        const duration<X_base, X_ratio>&    p_timeout)
+    {
+        using self_type             = X_self;
+        using derived_type          = typename std::decay_t<self_type>::derived_type;
+        using derived_storage_type  = storage_type_t<X_mode, derived_type>;
+        using derived_ref_type      = std::conditional_t<
+                                        std::is_const_v<std::remove_reference_t<self_type>>,
+                                        derived_type const &,
+                                        derived_type &>;
+        using derived_forward_type  = forward_type_t<X_mode, derived_ref_type>;
+        using timeout_type          = timing::timeout<derived_storage_type>;
+
+        auto& self = static_cast<derived_ref_type>(p_self);
+
+        return timeout_type(
+            std::forward<derived_forward_type>(self),
+            p_timeout);
+    }
+
+} }
+
+namespace asyncpp
+{
+
+    template<
+        typename T_value,
+        typename T_derived>
+    template<
+        chaining_mode X_mode,
+        typename X_base,
+        typename X_ratio>
+    auto base_stream<T_value, T_derived>
+        ::timeout(const duration<X_base, X_ratio>& p_timeout) &
+    {
+        return __stream::timeout_impl<X_mode>(std::move(*this), p_timeout);
+    }
+
+    template<
+        typename T_value,
+        typename T_derived>
+    template<
+        chaining_mode X_mode,
+        typename X_base,
+        typename X_ratio>
+    auto base_stream<T_value, T_derived>
+        ::timeout(const duration<X_base, X_ratio>& p_timeout) &&
+    {
+        static_assert(
+            X_mode != ref,
+            "Can not store rvalue reference as lvalue reference!");
+
+        return __stream::timeout_impl<X_mode>(std::move(*this), p_timeout);
+    }
+
+}
diff --git a/include/asyncpp/fs/directory.h b/include/asyncpp/fs/directory.h
index 88e6c0c..7749920 100644
--- a/include/asyncpp/fs/directory.h
+++ b/include/asyncpp/fs/directory.h
@@ -4,8 +4,7 @@
 
 #include <cppfs/path.h>
 
-#include <asyncpp/core/stream.pre.h>
-#include <asyncpp/core/future/lazy.h>
+#include <asyncpp/core/stream/stream.pre.h>
 
 namespace asyncpp {
 namespace fs {
diff --git a/include/asyncpp/timing/delay.h b/include/asyncpp/timing/delay.h
index fda6241..83609d2 100644
--- a/include/asyncpp/timing/delay.h
+++ b/include/asyncpp/timing/delay.h
@@ -1,7 +1,7 @@
 #pragma once
 
 #include <asyncpp/core/misc.h>
-#include <asyncpp/core/future.h>
+#include <asyncpp/core/future/future.h>
 
 #include "timer.h"
 #include "delay.pre.h"
diff --git a/include/asyncpp/timing/delay.inl b/include/asyncpp/timing/delay.inl
index 95d158e..3ead3de 100644
--- a/include/asyncpp/timing/delay.inl
+++ b/include/asyncpp/timing/delay.inl
@@ -1,8 +1,7 @@
 #pragma once
 
-#include <asyncpp/core/future.pre.h>
-#include <asyncpp/core/result.pre.h>
-#include <asyncpp/core/result.inl>
+#include <asyncpp/core/result.h>
+#include <asyncpp/core/future/future.pre.h>
 
 #include "delay.h"
 
diff --git a/include/asyncpp/timing/interval.h b/include/asyncpp/timing/interval.h
index 8d2f06e..f2a055d 100644
--- a/include/asyncpp/timing/interval.h
+++ b/include/asyncpp/timing/interval.h
@@ -1,8 +1,8 @@
 #pragma once
 
 #include <asyncpp/core/misc.h>
-#include <asyncpp/core/future.h>
-#include <asyncpp/core/stream.h>
+#include <asyncpp/core/future/future.h>
+#include <asyncpp/core/stream/stream.h>
 
 #include "delay.h"
 
diff --git a/include/asyncpp/timing/timeout.h b/include/asyncpp/timing/timeout.h
index 4fdc92b..cda3839 100644
--- a/include/asyncpp/timing/timeout.h
+++ b/include/asyncpp/timing/timeout.h
@@ -3,8 +3,8 @@
 #include <cppcore/misc/exception.h>
 
 #include <asyncpp/core/misc.h>
-#include <asyncpp/core/future.h>
-#include <asyncpp/core/stream.h>
+#include <asyncpp/core/future/future.h>
+#include <asyncpp/core/stream/stream.h>
 
 #include "delay.h"
 
diff --git a/test/asyncpp/timing/timeout_tests.cpp b/test/asyncpp/timing/timeout_tests.cpp
index 15204a5..c8d9792 100644
--- a/test/asyncpp/timing/timeout_tests.cpp
+++ b/test/asyncpp/timing/timeout_tests.cpp
@@ -141,7 +141,7 @@ TEST(timeout_tests, poll_stream_no_timeout)
 
     auto t = test_stream { 0 };
     auto f = t
-        .timeout(std::chrono::seconds(5));
+        .timeout<ref>(std::chrono::seconds(5));
 
     EXPECT_CALL(m, now())
         .WillOnce(Return(time_point(std::chrono::seconds(0))));
@@ -191,7 +191,7 @@ TEST(timeout_tests, poll_stream_timeout)
 
     auto t = test_stream { 0 };
     auto f = t
-        .timeout(std::chrono::seconds(5));
+        .timeout<ref>(std::chrono::seconds(5));
 
     EXPECT_CALL(m, now())
         .WillOnce(Return(time_point(std::chrono::seconds(0))));