The hymen is a membrane with a hole in the center that covers the outside of a woman’s vagina, and is located right at the vaginal opening, which is not very deep. The hymen is smaller and thicker before puberty, and as the body matures, the hymen of an adult woman is about 1-2mm thick, containing connective tissue, microvessels and nerve endings. In the center of the hymen, there is usually a small hole with a diameter of 1-1.5cm, known as the hymenal aperture, through which menstruation is discharged from the body. The shape of the hymen varies from person to person. During the first sexual intercourse, the hymen often ruptures and bleeds, which can be painful. Some hymens are more elastic and have a slightly larger hole, so they may not rupture during sex and will not rupture until the time of delivery. There are also hymens that are thicker and rupture will result in more bleeding and a longer bleeding time. There are also individual hymens without holes, belonging to the hymen atresia, which makes women unable to discharge menstrual blood during menstruation, and often found late menstruation during puberty, accompanied by cyclical pain in the abdomen, and the treatment is usually handled by hymenotomy.