The breast is one of two prominences located on the upper ventral region of the torso of primates. In females, it serves as the mammary gland, which produces and secretes milk to feed infants.
Both females and males develop breasts from the same embryological tissues. At puberty, estrogens, in conjunction with growth hormone, cause breast development in female humans and to a much lesser extent in other primates. Breast development in other primate females generally only occurs with pregnancy.