Gray matter is part of the tissue that makes up the central nervous system of humans and other vertebrates. It is brown-gray in color and consists largely of the cell bodies of neurons, branching dendrites, and glial cells. Gray matter is the site of coordination between nerves of the central nervous system. In the brain, it forms the outer layer of the cerebrum (the cerebral cortex) and the outer layer of the cerebellum. In the spinal cord, gray matter lies centrally and is surrounded by white matter.