Alveoli are grape like clusters of cells inside the breast that produce breast milk in response to the action of suckling from the infant. These alveoli encompass thin tubes called ducts that carry milk from the alveoli to the nipple. The areola is the dark area of skin around the nipple. Montgomery glands located on the areola produces natural oils to keep the nipple clean. When the infant suckles at the breast, a hormone response releases the milk from the alveoli into the ducts and is transfered to the infant through 4-9 openings in the nipple. The hormone responsible for this action is oxytocin. The sucking action of the infant in the process of feeding stimulates the hormone prolactin which stimulates milk production. Each time the infant nurses there is a surge of prolactin. The more often a baby nurses the higher the baseline level of prolactin. Four weeks after birth, there is a natural decline in prolactin levels and the production of milk is then based on supply and demand. The more often and completely the breast is emptied of milk, the more rapidly the breasts will produce milk. The production of milk is a fine balance between hormones and frequency of feedings, which is regulated by the infant.