The midbrain is the most rostral region of the mammalian brainstem, caudally adjoining the pons and rostrally adjoining the diencephalon. Notable structures of the midbrain include: substantia nigra, ventral tegmental area, part of the red nucleus, the dorsal and ventral raphe nuclei, the midbrain reticular formation, and the superior colliculus. The midbrain, along with the cerebellum, develops from the mesencephalon, differentiating it from the rest of the brainstem, which develops from the rhombencephalon.