Diencephalon:

Diencephalon (in red). Image courtesy of Life Science Databases (LSDB).

Diencephalon (in red). Image courtesy of Life Science Databases (LSDB).

literally "between-brain", the diencephalon is the area of the brain between the telencephalon and brainstem. It consists of the thalamus, subthalamus, hypothalamus, and epithalamus.