The mammary gland is an organ of ectodermal origin whose structure reflects its function: the production of milk for lactation. In humans, the breast has both an aesthetic value and an erotic relevance. The size and shape of women's breasts vary considerably. True symmetry does not exist in reality. Often one breast is slightly larger or smaller, higher or lower or shaped differently than the other. The inner structure of the mammary gland is made of an epithelial component that consists of lobules, where milk is made, which connect to ducts that lead out to the nipple. These lobules and ducts are located spread throughout the background fibrous tissue and adipose tissue that form the main mass of the breast.