The nipple, also known as the teat, is a cylindrical part of the central projection of the mammalian breast that is harder than the areola and the breast. The human female nipple is an important erogenous zone with the function of breastfeeding. The nipple is generated by tightly packed smooth muscle and connective tissue. when encountering sexual or mechanical stimulation, the smooth muscle contraction can make the nipple harden and bulge, the cylindrical part is generally 0.8cm-1.5cm, about 1.2cm-2cm above the areola level. when the nipple reaches the mature stage, the nipple is generally bulging out, unmarried and infertile women have smaller nipples. It is only after pregnancy that the breasts and nipples are affected by estrogen and progesterone in the pregnant woman’s body, and the nipples gradually increase in size and become raised. The size of nipple development varies from person to person and may be related to hormone levels. However, the size of the nipple does not necessarily mean that it develops in an abnormality. Large nipples can be operated on, and surgery is not necessary.