Brain cells. Fluorescence light micrograph of assorted brain cells. A typical nerve cell is seen at centre (green), with processes extending out into the surrounding tissue. Nerve cell processes are of two types: a single large axon (the output nerve fibre) which is seen extending to the left of the cell at centre, and many branching dendrites as smaller input processes that serve as sensory receptors. The brain is divided into two main regions, the grey and white matter. Grey matter (as here) in the brain consists mainly of cell bodies and branched dendrites. White matter is made up largely of nerve fibres connecting areas of grey matter. Magnification unknown.