The hypothalamus links the nervous system to the enocrine system via the pituitary gland (hypophysis). The hypothalamus, (from Greek ὑποθαλαμος = under the thalamus) is located below the thalamus, just above the brain stem. This brain region occupies the major portion of the ventral diencephalon. It is found in all mammalian brains. In humans, it is roughly the size of an almond.