Cerebellum Light micrograph of a crosssection through the cortex surface and medulla core of a human cerebellum part of the brain The cerebe llum is highly folded with fissures thick white lines between its ridges lobules The cortex has a molecular layer light blue which mainly consists of nerve fibre networks Beneath this is a layer of Purkinje nerve cells thin white lines This lies over the granular layer grainy black blue of nerve cells Beneath the cortex is the medulla black This consists of white matter large nerve fibres axons The cerebellum controls body posture coordinates muscle move ment balance Magnification x at xcm size