Here's a nice video showing Samsung's Super AMOLED display under a 100X microscope (the device is a Samsung Focus phone):

You can see that this display uses a PenTile subpixel matrix (in which the (smaller) green subpixel is shared between two pixels). Samsung's upcoming Super AMOLED Plus no longer uses a PenTile.

Merck - Advancing Display, Advancing LifeMerck - Advancing Display, Advancing Life