The phenomenon of male lactation in humans has become more common in recent years ue to the use of medications that stimulate a man's mammary glands. Though boys and men have nipples, many are unaware that they also have mammary glands. In ordinary circumstances, there is so little mammary tissue that it is unnoticeable; if the male breasts develop visibly, the condition is called gynecomastia. Under the appropriate hormonal stimulus—that nature provides to human females when they become pregnant and give birth—the mammary glands of human males can also produce milk. The volume of milk produced is low relative to that of a lactating female. Newborn baby boys (and girls) can occasionally produce milk because of the intense hormones involved in their mother's pregnancy and the hours of childbirth; this is called witch's milk.