The cerebellum is the largest structure of the hindbrain. It resides within the posterior cranial fossa and is composed of two large hemispheres, which are connected by the vermis in the midline (eFig. 9.61). Functionally, the cerebellum plays a role in maintaining balance and influencing posture and is responsible for coordinating movements by synchronizing contraction and relaxation of voluntary muscles. We will first examine the structural organization of the cerebellum and then review how these structures contribute to the circuitry of the cerebellum.