The hymen is a thin piece of tissue located at the opening of the vagina. It is formed by fragments of tissue left over from fetal development and is usually a ring-shaped piece of tissue that surrounds the vaginal opening when a person is born. However, the size, shape, and thickness of the hymen are unique to each person and can change over time. The hymen has no purpose and does not impact the body or reproductive system. Contrary to popular belief, the hymen is not a complete membrane covering the full vaginal opening, and it usually has a hole big enough for period blood to come out and for tampons to be used comfortably. The hymen can be stretched open the first time a person has vaginal sex, which might cause some pain or bleeding, but this doesnt happen to everyone. The hymen can also break or tear from other activities such as inserting a tampon, riding a bike, doing sports, or putting something in the vagina (like a finger or sex toy) . In rare cases, the hymen covers the entire vaginal opening, which is called an imperforate or microperforate hymen, and it can cause issues with menstruation. In these cases, the hymen can be surgically opened so that the person can have regular periods, use tampons, and have other kinds of vaginal penetration.