alpha mapping on 3D objects

[system]

Hi, I am trying to create a tree with alpha texture on the Unity iPhone. I tried to save on the Bitmap file with alpha channel on it. But when I import the texture onto the Unity, it just compressed to its own format and alpha channel is omitted. How can I setup texture for doing alpha mapping on the 3D object? Do I really need to use the shader? Does the unity have built in alpha channel detector?

Thanks

[system]

Sry.. Guys.. I already found the similar Question like this and the answer is below...

You have to set the "shader" setting in your material to a shader which supports transparency. They are grouped under the "Transparent" section of the shader pop up menu.