diff --git a/sandbox/ConsoleApp1/Program.cs b/sandbox/ConsoleApp1/Program.cs
index 1ce3d30e..40ea821c 100644
--- a/sandbox/ConsoleApp1/Program.cs
+++ b/sandbox/ConsoleApp1/Program.cs
@@ -30,7 +30,7 @@
 
 var range = System.Reactive.Linq.Observable.Range(1, 10);
 
-System.Reactive.Linq.Observable.Defer(
+
 
 // range.TakeLast(
 
@@ -42,6 +42,8 @@
 
 //var xs = await publisher.Take(TimeSpan.FromSeconds(5));
 
+
+
 foreach (var item in Enumerable.Range(1, 10).TakeWhile(x => x <= 3))
 {
     Console.WriteLine(item);
diff --git a/src/R3/Factories/Create.cs b/src/R3/Factories/Create.cs
new file mode 100644
index 00000000..7e023d97
--- /dev/null
+++ b/src/R3/Factories/Create.cs
@@ -0,0 +1,31 @@
+namespace R3;
+
+public static partial class Observable
+{
+    public static Observable<T> Create<T>(Func<Observer<T>, IDisposable> subscribe)
+    {
+        return new AnonymousObservable<T>(subscribe);
+    }
+
+    public static Observable<T> Create<T, TState>(TState state, Func<Observer<T>, TState, IDisposable> subscribe)
+    {
+        return new AnonymousObservable<T, TState>(state, subscribe);
+    }
+}
+
+internal sealed class AnonymousObservable<T>(Func<Observer<T>, IDisposable> subscribe) : Observable<T>
+{
+    protected override IDisposable SubscribeCore(Observer<T> observer)
+    {
+        return subscribe(observer);
+    }
+}
+
+internal sealed class AnonymousObservable<T, TState>(TState state, Func<Observer<T>, TState, IDisposable> subscribe) : Observable<T>
+{
+    protected override IDisposable SubscribeCore(Observer<T> observer)
+    {
+        return subscribe(observer, state);
+    }
+}
+
diff --git a/src/R3/Factories/_EventFactory.cs b/src/R3/Factories/_EventFactory.cs
deleted file mode 100644
index 64893424..00000000
--- a/src/R3/Factories/_EventFactory.cs
+++ /dev/null
@@ -1,16 +0,0 @@
-namespace R3;
-
-public static partial class Observable
-{
-    // TODO: this is working space, will remove this file after complete.
-
-    // TODO: Defer, DeferAsync, Start, Using, Create
-
-
-    // ToObservable(ToEvent)
-    // ToAsyncEnumerable?
-    // AsObservable
-    // AsSingleUnitObservable
-    // AsUnitObservable
-    // AsUniResult
-}
diff --git a/src/R3/ObserverExtensions.cs b/src/R3/ObserverExtensions.cs
index 682fff90..737c8a36 100644
--- a/src/R3/ObserverExtensions.cs
+++ b/src/R3/ObserverExtensions.cs
@@ -12,6 +12,12 @@ public static void OnCompleted<T>(this Observer<T> observer, Exception exception
         observer.OnCompleted(Result.Failure(exception));
     }
 
+    public static Observer<T> Wrap<T>(this Observer<T> observer)
+    {
+        return new WrappedObserver<T>(observer);
+    }
+
+
     public static Observer<T> ToObserver<T>(this IObserver<T> observer)
     {
         return new IObserverToObserver<T>(observer);
@@ -42,3 +48,26 @@ protected override void OnCompletedCore(Result result)
         }
     }
 }
+
+internal sealed class WrappedObserver<T>(Observer<T> observer) : Observer<T>
+{
+    protected override void OnNextCore(T value)
+    {
+        observer.OnNext(value);
+    }
+
+    protected override void OnErrorResumeCore(Exception error)
+    {
+        observer.OnErrorResume(error);
+    }
+
+    protected override void OnCompletedCore(Result result)
+    {
+        observer.OnCompleted(result);
+    }
+
+    protected override void DisposeCore()
+    {
+        observer.Dispose();
+    }
+}
diff --git a/src/R3/Operators/AsObservable.cs b/src/R3/Operators/AsObservable.cs
index 70874939..1bfed5ce 100644
--- a/src/R3/Operators/AsObservable.cs
+++ b/src/R3/Operators/AsObservable.cs
@@ -2,14 +2,33 @@
 
 public static partial class ObservableExtensions
 {
-    // TODO: more overload?
-    public static IObservable<T> AsObservable<T>(this Observable<T> source)
+    // TODO: test
+
+    public static Observable<T> AsObservable<T>(this Observable<T> source)
     {
+        if (source is AsObservable<T>) // already hide
+        {
+            return source;
+        }
+
         return new AsObservable<T>(source);
     }
+
+    public static IObservable<T> AsIObservable<T>(this Observable<T> source)
+    {
+        return new AsIObservable<T>(source);
+    }
+}
+
+internal sealed class AsObservable<T>(Observable<T> observable) : Observable<T>
+{
+    protected override IDisposable SubscribeCore(Observer<T> observer)
+    {
+        return observable.Subscribe(observer.Wrap());
+    }
 }
 
-internal sealed class AsObservable<T>(Observable<T> source) : IObservable<T>
+internal sealed class AsIObservable<T>(Observable<T> source) : IObservable<T>
 {
     public IDisposable Subscribe(IObserver<T> observer)
     {
diff --git a/src/R3/Operators/_Operators.cs b/src/R3/Operators/_Operators.cs
index a45a0e88..aeb28c28 100644
--- a/src/R3/Operators/_Operators.cs
+++ b/src/R3/Operators/_Operators.cs
@@ -5,6 +5,8 @@ public static partial class ObservableExtensions
     // TODO: this is working space, will remove this file after complete.
 
 
+    // AsUnitObservable
+
     // Time based
     // Frame based
     // OnErrorStop
diff --git a/tests/R3.Tests/FactoryTests/CreateTest.cs b/tests/R3.Tests/FactoryTests/CreateTest.cs
new file mode 100644
index 00000000..9bb30765
--- /dev/null
+++ b/tests/R3.Tests/FactoryTests/CreateTest.cs
@@ -0,0 +1,60 @@
+
+namespace R3.Tests.FactoryTests;
+
+public class CreateTest
+{
+    [Fact]
+    public void Create()
+    {
+        var source = Observable.Create<int>(observer =>
+        {
+            observer.OnNext(1);
+            observer.OnNext(10);
+            observer.OnNext(100);
+            observer.OnCompleted();
+            return Disposable.Empty;
+        });
+
+        source.ToLiveList().AssertEqual([1, 10, 100]);
+    }
+
+    [Fact]
+    public void CreateS()
+    {
+        using var publisher = new Subject<int>();
+        var source = Observable.Create<int, Subject<int>>(publisher, (observer, state) =>
+        {
+            return state.Subscribe(new Wrap<int>(observer));
+        });
+
+        using var list = source.ToLiveList();
+
+        publisher.OnNext(1);
+        list.AssertEqual([1]);
+        publisher.OnNext(10);
+        list.AssertEqual([1, 10]);
+        publisher.OnNext(100);
+        list.AssertEqual([1, 10, 100]);
+
+        publisher.OnCompleted();
+        list.AssertIsCompleted();
+    }
+}
+
+file class Wrap<T>(Observer<T> observer) : Observer<T>
+{
+    protected override void OnCompletedCore(Result result)
+    {
+        observer.OnCompleted(result);
+    }
+
+    protected override void OnErrorResumeCore(Exception error)
+    {
+        observer.OnErrorResume(error);
+    }
+
+    protected override void OnNextCore(T value)
+    {
+        observer.OnNext(value);
+    }
+}
diff --git a/tests/R3.Tests/FactoryTests/DeferTest.cs b/tests/R3.Tests/FactoryTests/DeferTest.cs
index ecfb7094..2fd490f2 100644
--- a/tests/R3.Tests/FactoryTests/DeferTest.cs
+++ b/tests/R3.Tests/FactoryTests/DeferTest.cs
@@ -21,3 +21,5 @@ public void Test()
         list.AssertEqual([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
     }
 }
+
+