|Diagram depicting the main subdivisions of the embryonic vertebrate brain. These regions will later differentiate into forebrain, midbrain and hindbrain structures.|
The prosencephalon (or forebrain), the mesencephalon (midbrain), and rhombencephalon (hindbrain) are the three primary portions of the brain of vertebrates. They develop very early during development of the central nervous system.
When the embryonic prosencephalon fails to divide the brain into two lobes, it results in a condition known as holoprosencephaly.
Prosencephalon Facts for Kids. Kiddle Encyclopedia.