Gallium.

And we can see as we go along using either carbon nanotubes or gallium arsenide, or Silicon the kinds of machines that we had to build and we're at the level now of 1 or 2 or on a good day 3 transistors

So what I mean by that is, when physics changes, or we move to smaller transistors, or we move from, let's say, silicon to gallium arsenide or some other implementation technology, that changes the bottom layer here, but we want to still be able to reuse a lot of the other work that we've done over the years.