Women with regular menstrual cycles are advised to perform a breast self-examination 14 days before each period to prevent some breast diseases. Self-examination can be divided into three steps: see, feel and squeeze. Look: face the mirror, both arms hang down naturally, both shoulders flat, observe whether the bilateral breasts are symmetrical, whether the skin surface has no abnormalities bilateral nipples are symmetrical, etc. Touch: Gently massage your breasts with your fingers, use your index finger, middle finger and ring finger to press down and feel for pain and lumps. Squeeze: Squeeze the nipple to see if there is any fluid flow. Breast cancer, hyperprolactinemia, intraductal papilloma, and mastitis may all have fluid flow.