The hindbrain, rhombencephalon (shaped like a rhombus) is a developmental categorization of portions of the central nervous system in vertebrates.

The metencephalon is composed of the pons and the cerebellum; it contains: Rhombomeres Rh8-Rh4 form the myelencephalon.

The myelencephalon forms the medulla oblongata in the adult brain; it contains: The hindbrain is homologous to a part of the arthropod brain known as the sub-oesophageal ganglion, in terms of the genes that it expresses and its position in between the brain and the nerve cord.

[2] It has been suggested that the hindbrain first evolved in the urbilaterian—the last common ancestor of chordates and arthropods—between 570 and 555 million years ago.

[2][3] A rare brain disease of the cerebellum is rhombencephalosynapsis characterized by an absent or partially formed vermis.