The hypothalamus lies posterior to the thalamus and superior to the brain stem. The anterior border of the hypothalamus is formed by the optic chiasm. It is composed primarily of gray matter. The hypothalamus networks with the pituitary gland to control hormones. It regulates homeostasis and is in control of important autonomic nervous system functions. It regulates sleep, sexual appetites, dietary appetites, body temperature, chemical balance, and emotions.