The cerebrum actually is made up of two hemispheres. And when you look superficially at the brain, you'll see a couple of really prominent sulky, gi-ry and fissures. So your brain is actually... Your cerebrum is actually separated. They're actually held together through these hard ways. The white matter tracks. That's an important point because if you were to cut into the cerebrum, you would see just with your eyes parts of the brain that look gray and parts that look white. This is what we term gray matter and white matter.