Nipple inversion is a common breast deformity, which can be categorized into congenital inversion and acquired inversion, usually acquired inversion is mostly related to diseases. 1. Congenital inversion. It is mainly a symptom caused by abnormal physiological development. When there are congenital developmental abnormalities of breast tissue, such as shortening of breast ducts, fibrotic contracture of part of the tissue, congenital dysplasia of nipple smooth muscle and so on, all of them can pull the nipple and thus lead to nipple inversion. 2. Acquired inversion. It is also called secondary nipple inversion, which may be caused by acquired dysplasia, related to wearing too tight underwear during adolescence; it may also be caused by diseases, such as inflammation, tumors and other diseases invading breast ducts, ligaments and other tissues, which will cause them to contract and pull the nipple, thus leading to nipple inversion. Nipple inversion may be caused by diseases or developmental abnormalities. It is recommended that the relevant people should consult the doctor in time to clarify the cause of the disease and decide the appropriate treatment according to the condition of nipple inversion.