Cerebellum. Light micrograph of a section through the cerebellum of the brain. The cerebellum comprises three main layers. The outer grey matter (cortex) comprises the molecular layer (pink) and the granular layer (dark purple). Within the grey matter is the white matter (dark pink). Purkinje cells exist at the junction of the molecular and granular layer. Magnification: x20 when printed at 10 centimetres wide.