Moles are common harmless skin lesions. Moles may be flat or protruding. They vary in color from pink flesh tones to dark brown or black. The number of moles a person has depends on genetic factors and on sun exposure; most people have 20-50 of them. Moles begin to grow in infancy but new ones can appear at any age, sometimes in crops. Moles may darken following sun exposure or during pregnancy. During adulthood they often lose their pigmentation, and may disappear in old age.