In the examples you've considered so far, the shapes have been completely opaque. However, Silverlight supports true transparency. That means if you layer several elements on top of one another and give them all varying layers of transparency, you'll see exactly what you expect. At its simplest, this feature gives you the ability to create graphical backgrounds that “show through” the elements you place on top. At its most complex, this feature lets you create multilayered animations and other effects.
There are several ways to make an element partly transparent: