The nipples squeeze out a little bit of clear water, which is medically known as nipple overflow, and 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, so that the nipples will have a clear, bright-colored liquid overflow. The pathological factor refers to breast diseases that cause nipple overflow, which can be manifested as yellowish or colorless fluid overflowing from the nipples when suffering from cystic hyperplasia of the breast. In the case of intraductal papilloma, the nipples may overflow with light red fluid, and when the nipples are squeezed, there may be bloody fluid overflow. And once the nipple overflows with bright red fluid, it should be highly suspected to have intraductal breast tumor. 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.