The unusual surface appearance of the cerebellum conceals the fact that the bulk of the structure is made up of a very tightly folded layer of gray matter, the cerebellar cortex. It has been estimated that if the human cerebellar cortex could be completely unfolded it would give rise to a layer of neural tissue about 1 meter long and 10 centimeters wide—a total surface area of 500-1000 square cm, all packed within a volume of 100-150 cubic cm.[4][5] Underneath the gray matter of the cortex lies white matter, made up largely of myelinated nerve fibers running to and from the cortex.