Grey and white matter. Coloured scanning electron micrograph (SEM) of the boundary between the grey and white matter in the human cerebellum. The grey matter (green) is made up of nerve bodies and their associated fibres. The bodies appear as small rounded masses in the tangle of fibres. The white matter (yellow) is almost entirely made up of the axons of nerve cells, and appears far more dense than the grey matter. The grey matter of the cerebellum is largely concerned with the control of posture and movement. The white matter beneath is mainly responsible for connecting relevant grey matter areas, allowing them to communicate" with each other. Magnification unknown."