diff --git a/Engine/Source/Editor/EditorApp.cpp b/Engine/Source/Editor/EditorApp.cpp
index d34497b8..068b9cfc 100644
--- a/Engine/Source/Editor/EditorApp.cpp
+++ b/Engine/Source/Editor/EditorApp.cpp
@@ -3,7 +3,6 @@
 #include "Application/Engine.h"
 #include "Display/CameraController.h"
 #include "ECWorld/SceneWorld.h"
-#include "ImGui/EditorImGuiViewport.h"
 #include "ImGui/ImGuiContextInstance.h"
 #include "ImGui/Localization.h"
 #include "ImGui/UILayers/DebugPanel.h"
@@ -48,6 +47,7 @@
 #include "UILayers/TestNodeEditor.h"
 #include "Window/Input.h"
 #include "Window/Window.h"
+#include "Window/WindowManager.h"
 
 #include <imgui/imgui.h>
 #define IMGUI_DEFINE_MATH_OPERATORS
@@ -80,6 +80,8 @@ void EditorApp::Init(engine::EngineInitArgs initArgs)
 		CD_ERROR("Failed to open CSV file");
 	}
 
+	m_pWindowManager = std::make_unique<engine::WindowManager>();
+
 	// Phase 1 - Splash
 	//		* Compile uber shader permutations automatically when initialization or detect changes
 	//		* Show compile progresses so it still needs to update ui
@@ -94,7 +96,7 @@ void EditorApp::Init(engine::EngineInitArgs initArgs)
 	
 	pSplashWindow->OnResize.Bind<engine::RenderContext, &engine::RenderContext::OnResize>(m_pRenderContext.get());
 	m_pMainWindow = pSplashWindow.get();
-	AddWindow(cd::MoveTemp(pSplashWindow));
+	m_pWindowManager->AddWindow(cd::MoveTemp(pSplashWindow));
 
 	InitEditorRenderers();
 	EditorRenderersWarmup();
@@ -124,29 +126,12 @@ void EditorApp::Shutdown()
 {
 }
 
-engine::Window* EditorApp::GetWindow(void* handle) const
-{
-	auto itWindow = m_mapWindows.find(handle);
-	return itWindow != m_mapWindows.end() ? itWindow->second.get() : nullptr;
-}
-
-void EditorApp::AddWindow(std::unique_ptr<engine::Window> pWindow)
-{
-	m_mapWindows[pWindow->GetHandle()] = cd::MoveTemp(pWindow);
-}
-
-void EditorApp::RemoveWindow(void* handle)
-{
-	assert(handle != m_pMainWindow->GetHandle());
-	m_mapWindows.erase(handle);
-}
-
 void EditorApp::InitEditorImGuiContext(engine::Language language)
 {
 	assert(GetMainWindow() && "Init window before imgui context");
 
 	const bool enableDock = true;
-	const bool enableViewport = true;
+	const bool enableViewport = false;
 	m_pEditorImGuiContext = std::make_unique<engine::ImGuiContextInstance>(GetMainWindow()->GetWidth(), GetMainWindow()->GetHeight(), enableDock, enableViewport);
 	RegisterImGuiUserData(m_pEditorImGuiContext.get());
 
@@ -163,12 +148,12 @@ void EditorApp::InitEditorImGuiContext(engine::Language language)
 	// Init viewport settings.
 	if (enableViewport)
 	{
-		m_pEditorImGuiViewport = std::make_unique<EditorImGuiViewport>(this, m_pRenderContext.get());
+		m_pEditorImGuiContext->InitViewport(m_pWindowManager.get(), m_pRenderContext.get());
 		ImGuiViewport* pMainViewport = ImGui::GetMainViewport();
 		assert(pMainViewport);
 		pMainViewport->PlatformHandle = GetMainWindow();
 		pMainViewport->PlatformHandleRaw = GetMainWindow()->GetHandle();
-		m_pEditorImGuiViewport->Update();
+		m_pEditorImGuiContext->UpdateViewport();
 	}
 }
 
@@ -601,22 +586,7 @@ bool EditorApp::Update(float deltaTime)
 		InitEngineUILayers();
 	}
 
-	for (auto& [_, pWindow] : m_mapWindows)
-	{
-		pWindow->Update();
-		if (pWindow->IsFocused())
-		{
-			m_pFocusedWindow = pWindow.get();
-		}
-	}
-
-	if (m_pEditorImGuiContext->IsViewportEnable())
-	{
-		m_pEditorImGuiViewport->Update();
-		auto position = engine::Input::Get().GetGloalMousePosition();
-		engine::Input::Get().SetMousePositionX(position.first);
-		engine::Input::Get().SetMousePositionY(position.second);
-	}
+	m_pWindowManager->Update();
 	m_pEditorImGuiContext->Update(deltaTime);
 	m_pSceneWorld->Update();
 
@@ -637,6 +607,12 @@ bool EditorApp::Update(float deltaTime)
 		}
 	}
 
+	if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+	{
+		ImGui::UpdatePlatformWindows();
+		ImGui::RenderPlatformWindowsDefault();
+	}
+
 	if (m_pEngineImGuiContext)
 	{
 		GetMainWindow()->SetMouseVisible(m_pSceneView->IsShowMouse(), m_pSceneView->GetMouseFixedPositionX(), m_pSceneView->GetMouseFixedPositionY());
diff --git a/Engine/Source/Editor/EditorApp.h b/Engine/Source/Editor/EditorApp.h
index 73da2374..91c0ebe0 100644
--- a/Engine/Source/Editor/EditorApp.h
+++ b/Engine/Source/Editor/EditorApp.h
@@ -14,6 +14,7 @@ class FlybyCamera;
 class ImGuiBaseLayer;
 class ImGuiContextInstance;
 class Window;
+class WindowManager;
 class RenderContext;
 class Renderer;
 class AABBRenderer;
@@ -28,7 +29,6 @@ struct ImGuiContext;
 namespace editor
 {
 
-class EditorImGuiViewport;
 class FileWatcher;
 class SceneView;
 
@@ -46,10 +46,8 @@ class EditorApp final : public engine::IApplication
 	virtual bool Update(float deltaTime) override;
 	virtual void Shutdown() override;
 
-	engine::Window* GetWindow(void* handle) const;
 	engine::Window* GetMainWindow() const { return m_pMainWindow; }
-	void AddWindow(std::unique_ptr<engine::Window> pWindow);
-	void RemoveWindow(void* handle);
+	engine::WindowManager* GetWindowManager() const { return m_pWindowManager.get(); }
 
 	void InitRenderContext(engine::GraphicsBackend backend, void* hwnd = nullptr);
 
@@ -90,16 +88,20 @@ class EditorApp final : public engine::IApplication
 
 	// Windows
 	engine::Window* m_pMainWindow = nullptr;
-	engine::Window* m_pFocusedWindow = nullptr;
-	std::map<void*, std::unique_ptr<engine::Window>> m_mapWindows;
+	std::unique_ptr<engine::WindowManager> m_pWindowManager;
 
 	// ImGui
 	std::unique_ptr<engine::ImGuiContextInstance> m_pEditorImGuiContext;
 	std::unique_ptr<engine::ImGuiContextInstance> m_pEngineImGuiContext;
-	std::unique_ptr<EditorImGuiViewport> m_pEditorImGuiViewport;
 
 	// Scene
 	std::unique_ptr<engine::SceneWorld> m_pSceneWorld;
+
+	// Rendering
+	std::unique_ptr<engine::RenderContext> m_pRenderContext;
+	std::unique_ptr<engine::ShaderCollections> m_pShaderCollections;
+	std::vector<std::unique_ptr<engine::Renderer>> m_pEditorRenderers;
+	std::vector<std::unique_ptr<engine::Renderer>> m_pEngineRenderers;
 	editor::SceneView* m_pSceneView = nullptr;
 	engine::Renderer* m_pSceneRenderer = nullptr;
 	engine::Renderer* m_pWhiteModelRenderer = nullptr;
@@ -109,13 +111,6 @@ class EditorApp final : public engine::IApplication
 	engine::Renderer* m_pTerrainRenderer = nullptr;
 	engine::Renderer* m_pAABBRenderer = nullptr;
 
-	// Rendering
-	std::unique_ptr<engine::RenderContext> m_pRenderContext;
-	std::unique_ptr<engine::ShaderCollections> m_pShaderCollections;
-
-	std::vector<std::unique_ptr<engine::Renderer>> m_pEditorRenderers;
-	std::vector<std::unique_ptr<engine::Renderer>> m_pEngineRenderers;
-
 	// Controllers for processing input events.
 	std::unique_ptr<engine::CameraController> m_pViewportCameraController;
 
diff --git a/Engine/Source/Editor/ImGui/EditorImGuiViewport.cpp b/Engine/Source/Editor/ImGui/EditorImGuiViewport.cpp
deleted file mode 100644
index 090d337d..00000000
--- a/Engine/Source/Editor/ImGui/EditorImGuiViewport.cpp
+++ /dev/null
@@ -1,97 +0,0 @@
-#include "EditorImGuiViewport.h"
-
-#include "EditorApp.h"
-#include "Rendering/RenderContext.h"
-#include "Window/Window.h"
-
-#include <imgui/imgui.h>
-
-namespace editor
-{
-
-EditorImGuiViewport::EditorImGuiViewport(editor::EditorApp* pEditor, engine::RenderContext* pRenderContext)
-{
-	static editor::EditorApp* pEditorApp = pEditor;
-
-	ImGuiPlatformIO& platformIO = ImGui::GetPlatformIO();
-	platformIO.Platform_CreateWindow = [](ImGuiViewport* pViewport)
-	{
-		auto pWindow = std::make_unique<engine::Window>("Dockable", 100, 100);
-		pViewport->PlatformHandle = pWindow.get();
-		pViewport->PlatformHandleRaw = pWindow->GetHandle();
-		pEditorApp->AddWindow(cd::MoveTemp(pWindow));
-	};
-	
-	platformIO.Platform_DestroyWindow = [](ImGuiViewport* pViewport)
-	{
-		pEditorApp->RemoveWindow(pViewport->PlatformHandleRaw);
-		pViewport->PlatformHandle = nullptr;
-		pViewport->PlatformUserData = nullptr;
-	};
-	
-	platformIO.Platform_ShowWindow = [](ImGuiViewport* pViewport)
-	{
-		pEditorApp->GetWindow(pViewport->PlatformHandleRaw)->Show();
-	};
-	
-	platformIO.Platform_SetWindowPos = [](ImGuiViewport* pViewport, ImVec2 v)
-	{
-		pEditorApp->GetWindow(pViewport->PlatformHandleRaw)->SetPosition(static_cast<int>(v.x), static_cast<int>(v.y));
-	};
-	
-	platformIO.Platform_GetWindowPos = [](ImGuiViewport* pViewport) -> ImVec2
-	{
-		engine::Window* pWindow = pEditorApp->GetWindow(pViewport->PlatformHandleRaw);
-		auto position = pWindow->GetPosition();
-		return { static_cast<float>(position.first), static_cast<float>(position.second) };
-	};
-	
-	platformIO.Platform_SetWindowSize = [](ImGuiViewport* pViewport, ImVec2 v)
-	{
-		pEditorApp->GetWindow(pViewport->PlatformHandleRaw)->SetSize(static_cast<int>(v.x), static_cast<int>(v.y));
-	};
-	
-	platformIO.Platform_GetWindowSize = [](ImGuiViewport* pViewport) -> ImVec2
-	{
-		engine::Window* pWindow = pEditorApp->GetWindow(pViewport->PlatformHandleRaw);
-		auto size = pWindow->GetSize();
-		return { static_cast<float>(size.first), static_cast<float>(size.second) };
-	};
-	
-	platformIO.Platform_SetWindowTitle = [](ImGuiViewport* pViewport, const char* pTitle)
-	{
-		engine::Window* pWindow = pEditorApp->GetWindow(pViewport->PlatformHandleRaw);
-		pWindow->SetTitle(pTitle);
-	};
-}
-
-void EditorImGuiViewport::Update()
-{
-	ImGuiPlatformIO& platformIO = ImGui::GetPlatformIO();
-	int monitorCount = engine::Window::GetDisplayMonitorCount();
-	platformIO.Monitors.resize(0);
-	for (int monitorIndex = 0; monitorIndex < monitorCount; ++monitorIndex)
-	{
-		auto mainRect = engine::Window::GetDisplayMonitorMainRect(monitorIndex);
-		auto workRect = engine::Window::GetDisplayMonitorWorkRect(monitorIndex);
-
-		ImGuiPlatformMonitor monitor;
-		monitor.MainPos = ImVec2((float)mainRect.x, (float)mainRect.y);
-		monitor.MainSize = ImVec2((float)mainRect.w, (float)mainRect.h);
-		monitor.WorkPos = ImVec2((float)workRect.x, (float)workRect.y);
-		monitor.WorkSize = ImVec2((float)workRect.w, (float)workRect.h);
-
-		// Check if the display's position is at (0,0), which is typical for the primary display.
-		bool isPrimaryDisplay = mainRect.x == 0 && mainRect.y == 0;
-		if (isPrimaryDisplay)
-		{
-			platformIO.Monitors.push_front(monitor);
-		}
-		else
-		{
-			platformIO.Monitors.push_back(monitor);
-		}
-	}
-}
-
-}
\ No newline at end of file
diff --git a/Engine/Source/Editor/ImGui/EditorImGuiViewport.h b/Engine/Source/Editor/ImGui/EditorImGuiViewport.h
deleted file mode 100644
index 21c494ed..00000000
--- a/Engine/Source/Editor/ImGui/EditorImGuiViewport.h
+++ /dev/null
@@ -1,33 +0,0 @@
-#pragma once
-
-namespace engine
-{
-
-class RenderContext;
-
-}
-
-namespace editor
-{
-
-class EditorApp;
-
-struct EditorImGuiViewportData
-{
-	engine::RenderContext* pRenderContext;
-};
-
-class EditorImGuiViewport
-{
-public:
-	EditorImGuiViewport() = delete;
-	explicit EditorImGuiViewport(editor::EditorApp* pEditor, engine::RenderContext* pRenderContext);
-	EditorImGuiViewport(const EditorImGuiViewport&) = delete;
-	EditorImGuiViewport& operator=(const EditorImGuiViewport&) = delete;
-	EditorImGuiViewport(EditorImGuiViewport&&) = default;
-	EditorImGuiViewport& operator=(EditorImGuiViewport&&) = default;
-
-	void Update();
-};
-
-}
\ No newline at end of file
diff --git a/Engine/Source/Runtime/Application/Engine.cpp b/Engine/Source/Runtime/Application/Engine.cpp
index cfcdcda9..058c0114 100644
--- a/Engine/Source/Runtime/Application/Engine.cpp
+++ b/Engine/Source/Runtime/Application/Engine.cpp
@@ -27,7 +27,6 @@ Engine::~Engine()
 void Engine::Init(EngineInitArgs args)
 {
 	CD_ENGINE_INFO("Init engine");
-	Window::Init();
 
 	m_pApplication->Init(args);
 }
@@ -54,7 +53,6 @@ void Engine::Run()
 
 void Engine::Shutdown()
 {
-	Window::Shutdown();
 }
 
 //
diff --git a/Engine/Source/Runtime/ImGui/ImGuiContextInstance.cpp b/Engine/Source/Runtime/ImGui/ImGuiContextInstance.cpp
index f49e3dae..de33b7e2 100644
--- a/Engine/Source/Runtime/ImGui/ImGuiContextInstance.cpp
+++ b/Engine/Source/Runtime/ImGui/ImGuiContextInstance.cpp
@@ -3,8 +3,11 @@
 #include "IconFont/IconsMaterialDesignIcons.h"
 #include "IconFont/MaterialDesign.inl"
 #include "ImGui/ImGuiBaseLayer.h"
+#include "Rendering/RenderContext.h"
+#include "Rendering/RenderTarget.h"
 #include "Window/Input.h"
 #include "Window/Window.h"
+#include "Window/WindowManager.h"
 #include "Log/Log.h"
 
 #include <bgfx/bgfx.h>
@@ -16,7 +19,7 @@
 #include <misc/freetype/imgui_freetype.h>
 #endif
 
-//#include <format>
+#include <format>
 #include <string>
 #include <unordered_map>
 
@@ -176,8 +179,7 @@ class TempSwitchContextScope
 namespace engine
 {
 
-ImGuiContextInstance::ImGuiContextInstance(uint16_t width, uint16_t height, bool enableDock, bool enableViewport) :
-	m_enableViewport(enableViewport)
+ImGuiContextInstance::ImGuiContextInstance(uint16_t width, uint16_t height, bool enableDock, bool enableViewport)
 {
 	m_pImGuiContext = ImGui::CreateContext();
 	SwitchCurrentContext();
@@ -239,6 +241,139 @@ void ImGuiContextInstance::ClearUILayers()
 	m_pImGuiDockableLayers.clear();
 }
 
+void ImGuiContextInstance::InitViewport(WindowManager* pWindowManager, RenderContext* pRenderContext)
+{
+	// Register window interfaces.
+	static WindowManager* s_pWindowManager = pWindowManager;
+	ImGuiPlatformIO& platformIO = ImGui::GetPlatformIO();
+	platformIO.Platform_CreateWindow = [](ImGuiViewport* pViewport)
+	{
+		auto pWindow = std::make_unique<engine::Window>("ViewportWindow", 1, 1);
+		pViewport->PlatformHandle = pWindow.get();
+		pViewport->PlatformHandleRaw = pWindow->GetHandle();
+		s_pWindowManager->AddWindow(cd::MoveTemp(pWindow));
+	};
+
+	platformIO.Platform_DestroyWindow = [](ImGuiViewport* pViewport)
+	{
+		s_pWindowManager->RemoveWindow(pViewport->PlatformHandleRaw);
+		pViewport->PlatformHandle = nullptr;
+		pViewport->PlatformUserData = nullptr;
+	};
+
+	platformIO.Platform_ShowWindow = [](ImGuiViewport* pViewport)
+	{
+		s_pWindowManager->GetWindow(pViewport->PlatformHandleRaw)->Show();
+	};
+
+	platformIO.Platform_SetWindowPos = [](ImGuiViewport* pViewport, ImVec2 v)
+	{
+		s_pWindowManager->GetWindow(pViewport->PlatformHandleRaw)->SetPosition(static_cast<int>(v.x), static_cast<int>(v.y));
+	};
+
+	platformIO.Platform_GetWindowPos = [](ImGuiViewport* pViewport) -> ImVec2
+	{
+		engine::Window* pWindow = s_pWindowManager->GetWindow(pViewport->PlatformHandleRaw);
+		auto position = pWindow->GetPosition();
+		return { static_cast<float>(position.first), static_cast<float>(position.second) };
+	};
+
+	platformIO.Platform_SetWindowSize = [](ImGuiViewport* pViewport, ImVec2 v)
+	{
+		s_pWindowManager->GetWindow(pViewport->PlatformHandleRaw)->SetSize(static_cast<int>(v.x), static_cast<int>(v.y));
+	};
+
+	platformIO.Platform_GetWindowSize = [](ImGuiViewport* pViewport) -> ImVec2
+	{
+		engine::Window* pWindow = s_pWindowManager->GetWindow(pViewport->PlatformHandleRaw);
+		auto size = pWindow->GetSize();
+		return { static_cast<float>(size.first), static_cast<float>(size.second) };
+	};
+
+	platformIO.Platform_SetWindowTitle = [](ImGuiViewport* pViewport, const char* pTitle)
+	{
+		engine::Window* pWindow = s_pWindowManager->GetWindow(pViewport->PlatformHandleRaw);
+		pWindow->SetTitle(pTitle);
+	};
+
+	platformIO.Platform_GetWindowFocus = [](ImGuiViewport* pViewport)
+	{
+		engine::Window* pWindow = s_pWindowManager->GetWindow(pViewport->PlatformHandleRaw);
+		return pWindow->IsFocused();
+	};
+	
+	platformIO.Platform_SetWindowFocus = [](ImGuiViewport* pViewport)
+	{
+		engine::Window* pWindow = s_pWindowManager->GetWindow(pViewport->PlatformHandleRaw);
+		return pWindow->SetFocused();
+	};
+
+	// Register rendering interfaces.
+	static RenderContext* s_pRenderContext = pRenderContext;
+	platformIO.Renderer_CreateWindow = [](ImGuiViewport* pViewport)
+	{
+		uint16_t newViewID = s_pRenderContext->CreateView();
+		engine::StringCrc newRenderTargetName(std::format("ViewportRT_{}", newViewID));
+		s_pRenderContext->CreateRenderTarget(newRenderTargetName, 1, 1, pViewport->PlatformHandleRaw);
+		pViewport->PlatformUserData = reinterpret_cast<void*>(newViewID);
+	};
+
+	struct CastPtrToViewID
+	{
+		union
+		{
+			void* pUserData;
+			uint16_t viewID;
+		};
+	};
+
+	platformIO.Renderer_DestroyWindow = [](ImGuiViewport* pViewport)
+	{
+		CastPtrToViewID cast;
+		cast.pUserData = pViewport->PlatformUserData;
+		uint16_t viewID = cast.viewID;
+		s_pRenderContext->DestoryRenderTarget(StringCrc(std::format("ViewportRT_{}", viewID)));
+	};
+
+	platformIO.Renderer_SetWindowSize = [](ImGuiViewport* pViewport, ImVec2 size)
+	{
+		CastPtrToViewID cast;
+		cast.pUserData = pViewport->PlatformUserData;
+		uint16_t viewID = cast.viewID;
+		auto* pRenderTarget = s_pRenderContext->GetRenderTarget(StringCrc(std::format("ViewportRT_{}", viewID)));
+		pRenderTarget->Resize(static_cast<uint16_t>(size.x), static_cast<uint16_t>(size.y));
+	};
+}
+
+void ImGuiContextInstance::UpdateViewport()
+{
+	ImGuiPlatformIO& platformIO = ImGui::GetPlatformIO();
+	int monitorCount = engine::Window::GetDisplayMonitorCount();
+	platformIO.Monitors.resize(0);
+	for (int monitorIndex = 0; monitorIndex < monitorCount; ++monitorIndex)
+	{
+		auto mainRect = engine::Window::GetDisplayMonitorMainRect(monitorIndex);
+		auto workRect = engine::Window::GetDisplayMonitorWorkRect(monitorIndex);
+
+		ImGuiPlatformMonitor monitor;
+		monitor.MainPos = ImVec2((float)mainRect.x, (float)mainRect.y);
+		monitor.MainSize = ImVec2((float)mainRect.w, (float)mainRect.h);
+		monitor.WorkPos = ImVec2((float)workRect.x, (float)workRect.y);
+		monitor.WorkSize = ImVec2((float)workRect.w, (float)workRect.h);
+
+		// Check if the display's position is at (0,0), which is typical for the primary display.
+		bool isPrimaryDisplay = mainRect.x == 0 && mainRect.y == 0;
+		if (isPrimaryDisplay)
+		{
+			platformIO.Monitors.push_front(monitor);
+		}
+		else
+		{
+			platformIO.Monitors.push_back(monitor);
+		}
+	}
+}
+
 void ImGuiContextInstance::BeginDockSpace()
 {
 	// To create a dock space, we need to create a window to host it at first.
@@ -325,7 +460,16 @@ void ImGuiContextInstance::Update(float deltaTime)
 	SwitchCurrentContext();
 
 	auto& io = ImGui::GetIO();
-	
+
+	if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+	{
+		UpdateViewport();
+
+		auto position = engine::Input::Get().GetGloalMousePosition();
+		engine::Input::Get().SetMousePositionX(position.first);
+		engine::Input::Get().SetMousePositionY(position.second);
+	}
+
 	// It is necessary to pass correct deltaTime to ImGui underlaying framework because it will use the value to check
 	// something such as if mouse button double click happens(Two click event happens in one frame, < deltaTime).
 	io.DeltaTime = deltaTime;
diff --git a/Engine/Source/Runtime/ImGui/ImGuiContextInstance.h b/Engine/Source/Runtime/ImGui/ImGuiContextInstance.h
index e041be43..20af585e 100644
--- a/Engine/Source/Runtime/ImGui/ImGuiContextInstance.h
+++ b/Engine/Source/Runtime/ImGui/ImGuiContextInstance.h
@@ -14,6 +14,8 @@ namespace engine
 {
 
 class ImGuiBaseLayer;
+class WindowManager;
+class RenderContext;
 class SceneWorld;
 
 class ImGuiContextInstance
@@ -27,43 +29,37 @@ class ImGuiContextInstance
 	ImGuiContextInstance& operator=(ImGuiContextInstance&&) = default;
 	virtual ~ImGuiContextInstance();
 
-	// ImGui can have multiple ImGuiContexts. For example, you want to render ImGui both in engine and editor.
-	// This method helps to switch ImGui's current context pointer to this ImGuiContextInstance.
-	// Note that if a method needs to call ImGui api, please call this method in the first line
-	// unless you really know what you are doing.
-	// Update multiple ImGuiContext in different threads is not safe. So please update them both in main thread by correct order.
-	void SwitchCurrentContext() const;
+	void Update(float deltaTime);
 
-	// Query if m_pImGuiContext is current active context.
+	// Context settings.
 	bool IsActive() const;
+	void SwitchCurrentContext() const;
 
-	// Static layer means non-movable, non-dockable.
+	// GUI management.
+	void OnResize(uint16_t width, uint16_t height);
 	void AddStaticLayer(std::unique_ptr<ImGuiBaseLayer> pLayer);
-
-	// Dockable layer means movable, dockable.
 	std::vector<std::unique_ptr<ImGuiBaseLayer>>& GetDockableLayers() { return m_pImGuiDockableLayers; }
 	void AddDynamicLayer(std::unique_ptr<ImGuiBaseLayer> pLayer);
-    
 	void ClearUILayers();
 
-	void Update(float deltaTime);
-
-	void OnResize(uint16_t width, uint16_t height);
-
+	// GUI styles.
 	void LoadFontFiles(const std::vector<std::string>& ttfFileNames, engine::Language language);
 	ThemeColor GetImGuiThemeColor() const { return m_themeColor; }
+	void SetImGuiThemeColor(ThemeColor theme);
 	Language GetImGuiLanguage() const { return m_language; }
 	void SetImGuiLanguage(Language language);
 
-	void SetImGuiThemeColor(ThemeColor theme);
-
+	// Input management.
 	void SetWindowPosOffset(float x, float y) { m_windowPosOffsetX = x; m_windowPosOffsetY = y; }
 
+	// Viewport feature.
+	void InitViewport(WindowManager* pWindowManager, RenderContext* pRenderContext);
+	void UpdateViewport();
+
+	// Access to world data.
 	void SetSceneWorld(SceneWorld* pSceneWorld) { m_pSceneWorld = pSceneWorld; }
 	SceneWorld* GetSceneWorld() const { return m_pSceneWorld; }
 
-	bool IsViewportEnable() const { return m_enableViewport; }
-
 private:
 	void AddInputEvent();
 	void SetImGuiStyles();
@@ -86,7 +82,6 @@ class ImGuiContextInstance
 	float m_lastMousePositionX = 0.0f;
 	float m_lastMousePositionY = 0.0f;
 
-	bool m_enableViewport = false;
 	std::vector<std::unique_ptr<ImGuiBaseLayer>> m_pImGuiStaticLayers;
 	std::vector<std::unique_ptr<ImGuiBaseLayer>> m_pImGuiDockableLayers;
 };
diff --git a/Engine/Source/Runtime/Rendering/ImGuiRenderer.cpp b/Engine/Source/Runtime/Rendering/ImGuiRenderer.cpp
index a357ed54..096bd742 100644
--- a/Engine/Source/Runtime/Rendering/ImGuiRenderer.cpp
+++ b/Engine/Source/Runtime/Rendering/ImGuiRenderer.cpp
@@ -5,6 +5,8 @@
 
 #include <imgui/imgui.h>
 
+#include <format>
+
 namespace engine
 {
 
@@ -12,8 +14,6 @@ void ImGuiRenderer::Init()
 {
 	constexpr StringCrc programCrc = StringCrc("ImGuiProgram");
 	GetRenderContext()->RegisterShaderProgram(programCrc, { "vs_imgui", "fs_imgui" });
-
-	bgfx::setViewName(GetViewID(), "ImGuiRenderer");
 }
 
 void ImGuiRenderer::Warmup()
@@ -56,31 +56,58 @@ void ImGuiRenderer::UpdateView(const float* pViewMatrix, const float* pProjectio
 	}
 
 	ImGui::Render();
-	ImGui::UpdatePlatformWindows();
-	ImGui::RenderPlatformWindowsDefault();
 
-	bgfx::setViewMode(GetViewID(), bgfx::ViewMode::Sequential);
-	if (const engine::RenderTarget* pRenderTarget = GetRenderTarget())
+	struct CastPtrToViewID
 	{
-		bgfx::setViewFrameBuffer(GetViewID(), *(pRenderTarget->GetFrameBufferHandle()));
-	}
-
-	const ImDrawData* pImGuiDrawData = ImGui::GetDrawData();
-	float x = pImGuiDrawData->DisplayPos.x;
-	float y = pImGuiDrawData->DisplayPos.y;
-	float width = pImGuiDrawData->DisplaySize.x;
-	float height = pImGuiDrawData->DisplaySize.y;
-	const bgfx::Caps* pCapabilities = bgfx::getCaps();
+		union
+		{
+			void* pUserData;
+			uint16_t viewID;
+		};
+	};
 
-	cd::Matrix4x4 orthoMatrix = cd::Matrix4x4::Orthographic(x, x + width, y, y + height, 0.0f, 1000.0f, 0.0f, pCapabilities->homogeneousDepth);
-	bgfx::setViewRect(GetViewID(), 0, 0, uint16_t(width), uint16_t(height));
-	bgfx::setViewTransform(GetViewID(), nullptr, orthoMatrix.begin());
+	ImGuiPlatformIO& platformIO = ImGui::GetPlatformIO();
+	for (const ImGuiViewport* pViewport : platformIO.Viewports)
+	{
+		CastPtrToViewID cast;
+		cast.pUserData = pViewport->PlatformUserData;
+		uint16_t viewID = cast.viewID;
+		RenderTarget* pRenderTarget = GetRenderContext()->GetRenderTarget(StringCrc(std::format("ViewportRT_{}", viewID)));
+		if (!pRenderTarget)
+		{
+			viewID = GetViewID();
+		}
+		else
+		{
+			bgfx::setViewFrameBuffer(viewID, *pRenderTarget->GetFrameBufferHandle());
+		}
+		
+		bgfx::setViewName(viewID, "ImGuiRenderer");
+		bgfx::setViewMode(viewID, bgfx::ViewMode::Sequential);
+		
+		const ImDrawData* pImGuiDrawData = pViewport->DrawData;
+		float x = pImGuiDrawData->DisplayPos.x;
+		float y = pImGuiDrawData->DisplayPos.y;
+		float width = pImGuiDrawData->DisplaySize.x;
+		float height = pImGuiDrawData->DisplaySize.y;
+		const bgfx::Caps* pCapabilities = bgfx::getCaps();
+		cd::Matrix4x4 orthoMatrix = cd::Matrix4x4::Orthographic(x, x + width, y, y + height, 0.0f, 1000.0f, 0.0f, pCapabilities->homogeneousDepth);
+		bgfx::setViewRect(viewID, 0, 0, uint16_t(width), uint16_t(height));
+		bgfx::setViewTransform(viewID, nullptr, orthoMatrix.begin());
+	}
 }
 
 void ImGuiRenderer::Render(float deltaTime)
 {
-	ImDrawData* pImGuiDrawData = ImGui::GetDrawData();
+	ImGuiPlatformIO& platformIO = ImGui::GetPlatformIO();
+	for (const ImGuiViewport* pViewport : platformIO.Viewports)
+	{
+		RenderDrawData(pViewport->DrawData, deltaTime);
+	}
+}
 
+void ImGuiRenderer::RenderDrawData(ImDrawData* pImGuiDrawData, float deltaTime)
+{
 	int frameBufferWidth = static_cast<int>(pImGuiDrawData->DisplaySize.x * pImGuiDrawData->FramebufferScale.x);
 	int frameBufferHeight = static_cast<int>(pImGuiDrawData->DisplaySize.y * pImGuiDrawData->FramebufferScale.y);
 	const ImVec2 clipPos = pImGuiDrawData->DisplayPos;			// (0,0) unless using multi-viewports
diff --git a/Engine/Source/Runtime/Rendering/ImGuiRenderer.h b/Engine/Source/Runtime/Rendering/ImGuiRenderer.h
index 7ade340d..db326532 100644
--- a/Engine/Source/Runtime/Rendering/ImGuiRenderer.h
+++ b/Engine/Source/Runtime/Rendering/ImGuiRenderer.h
@@ -2,6 +2,8 @@
 
 #include "Rendering/Renderer.h"
 
+struct ImDrawData;
+
 namespace engine
 {
 
@@ -14,6 +16,9 @@ class ImGuiRenderer final : public engine::Renderer
 	virtual void Warmup() override;
 	virtual void UpdateView(const float* pViewMatrix, const float* pProjectionMatrix) override;
 	virtual void Render(float deltaTime) override;
+
+private:
+	void RenderDrawData(ImDrawData* pImGuiDrawData, float deltaTime);
 };
 
 }
\ No newline at end of file
diff --git a/Engine/Source/Runtime/Window/Window.cpp b/Engine/Source/Runtime/Window/Window.cpp
index 58a08157..481fb09b 100644
--- a/Engine/Source/Runtime/Window/Window.cpp
+++ b/Engine/Source/Runtime/Window/Window.cpp
@@ -65,17 +65,6 @@ Window::~Window()
 	SDL_DestroyWindow(m_pSDLWindow);
 }
 
-void Window::Close(bool bPushSdlEvent)
-{
-	m_isClosed = true;
-	if (!bPushSdlEvent) { return; }
-
-	SDL_Event sdlEvent;
-	SDL_QuitEvent& quitEvent = sdlEvent.quit;
-	quitEvent.type = SDL_QUIT;
-	SDL_PushEvent(&sdlEvent);
-}
-
 void* Window::GetHandle() const
 {
 	SDL_SysWMinfo wmi;
@@ -193,6 +182,27 @@ bool Window::GetMouseFocus() const
 	return SDL_GetWindowFlags(m_pSDLWindow) & SDL_WINDOW_MOUSE_FOCUS;
 }
 
+bool Window::IsFocused() const
+{
+	return SDL_GetWindowFlags(m_pSDLWindow) & SDL_WINDOW_INPUT_FOCUS;
+}
+
+void Window::SetFocused()
+{
+	SDL_RaiseWindow(m_pSDLWindow);
+}
+
+void Window::Close(bool bPushSdlEvent)
+{
+	m_isClosed = true;
+	if (!bPushSdlEvent) { return; }
+
+	SDL_Event sdlEvent;
+	SDL_QuitEvent& quitEvent = sdlEvent.quit;
+	quitEvent.type = SDL_QUIT;
+	SDL_PushEvent(&sdlEvent);
+}
+
 void Window::SetResizeable(bool on)
 {
 	SDL_SetWindowResizable(m_pSDLWindow, static_cast<SDL_bool>(on));
@@ -271,8 +281,6 @@ void Window::Update()
 {
 	Input::Get().Reset();
 
-	m_isFocused = SDL_GetWindowFlags(m_pSDLWindow) & SDL_WINDOW_INPUT_FOCUS;
-
 	SDL_Event sdlEvent;
 	while (SDL_PollEvent(&sdlEvent))
 	{
diff --git a/Engine/Source/Runtime/Window/Window.h b/Engine/Source/Runtime/Window/Window.h
index d3fd2b28..7f4961fb 100644
--- a/Engine/Source/Runtime/Window/Window.h
+++ b/Engine/Source/Runtime/Window/Window.h
@@ -36,7 +36,6 @@ class Window
     ~Window();
     
     void* GetHandle() const;
-    //void* GetParentHandle() const;
 
     const char* GetTitle() const;
     void SetTitle(const char* pTitle);
@@ -55,8 +54,16 @@ class Window
     void Hide();
     void SetFullScreen(bool on);
 
+    // Status
+    bool IsFocused() const;
+    void SetFocused();
     bool GetInputFocus() const;
     bool GetMouseFocus() const;
+
+    bool ShouldClose() const { return m_isClosed; }
+    void Close(bool bPushSdlEvent = true);
+
+    // Styles
     void SetResizeable(bool on);
     void SetBordedLess(bool on);
     void SetWindowIcon(const char* pFilePath) const;
@@ -65,19 +72,14 @@ class Window
 
     void Update();
 
-    bool IsFocused() const { return m_isFocused; }
-
-    bool ShouldClose() const { return m_isClosed; }
-    void Close(bool bPushSdlEvent = true);
 public:
-    // Window
+    // Delegates
     Delegate<void(const char*)> OnDropFile;
     MulticastDelegate<void(uint16_t, uint16_t)> OnResize;
 
 private:
     SDL_Window* m_pSDLWindow = nullptr;
     bool m_isClosed = false;
-    bool m_isFocused = false;
 };
 
 }
\ No newline at end of file
diff --git a/Engine/Source/Runtime/Window/WindowManager.cpp b/Engine/Source/Runtime/Window/WindowManager.cpp
new file mode 100644
index 00000000..d8a5d1e1
--- /dev/null
+++ b/Engine/Source/Runtime/Window/WindowManager.cpp
@@ -0,0 +1,45 @@
+#include "WindowManager.h"
+
+#include "Base/Template.h"
+#include "Window.h"
+
+#include <cassert>
+
+namespace engine
+{
+
+WindowManager::WindowManager()
+{
+	Window::Init();
+}
+
+WindowManager::~WindowManager()
+{
+	Window::Shutdown();
+}
+
+Window* WindowManager::GetWindow(void* handle) const
+{
+	auto itWindow = m_mapWindows.find(handle);
+	return itWindow != m_mapWindows.end() ? itWindow->second.get() : nullptr;
+}
+
+void WindowManager::AddWindow(std::unique_ptr<Window> pWindow)
+{
+	m_mapWindows[pWindow->GetHandle()] = cd::MoveTemp(pWindow);
+}
+
+void WindowManager::RemoveWindow(void* handle)
+{
+	m_mapWindows.erase(handle);
+}
+
+void WindowManager::Update()
+{
+	for (auto& [_, pWindow] : m_mapWindows)
+	{
+		pWindow->Update();
+	}
+}
+
+}
\ No newline at end of file
diff --git a/Engine/Source/Runtime/Window/WindowManager.h b/Engine/Source/Runtime/Window/WindowManager.h
new file mode 100644
index 00000000..258dcf04
--- /dev/null
+++ b/Engine/Source/Runtime/Window/WindowManager.h
@@ -0,0 +1,31 @@
+#pragma once
+
+#include <map>
+#include <memory>
+
+namespace engine
+{
+
+class Window;
+
+class WindowManager final
+{
+public:
+	WindowManager();
+	WindowManager(const WindowManager&) = delete;
+	WindowManager& operator=(const WindowManager&) = delete;
+	WindowManager(WindowManager&&) = default;
+	WindowManager& operator=(WindowManager&&) = default;
+	~WindowManager();
+
+	engine::Window* GetWindow(void* handle) const;
+	void AddWindow(std::unique_ptr<engine::Window> pWindow);
+	void RemoveWindow(void* handle);
+
+	void Update();
+
+private:
+	std::map<void*, std::unique_ptr<engine::Window>> m_mapWindows;
+};
+
+}
\ No newline at end of file