Nipple discharge is medically known as nipple overflow, and nipple overflow can be divided into physiological and pathological factors. Physiological factors refer to the increase in the level of estrogen and the growth of breast ducts during the physiological period or the growth period, resulting in the overflow of bright-colored liquid from the nipples. The pathological factors mostly refer to breast diseases that cause nipple overflow, which can be manifested as yellowish or colorless liquid overflow from the nipple when suffering from cystic hyperplasia, light red liquid overflow from the nipple when suffering from intraductal papilloma, and bloody liquid overflow when squeezing the nipple, while once the nipple overflows with bright red liquid, malignant tumor of the breast should be highly suspected. In conclusion, there are various causes of nipple overflow, and when nipple overflow occurs, you should go to a regular hospital for breast surgery or general surgery to identify the cause and actively treat it.