What Is the Hymen?
The hymen is a piece of tissue that, during development, blocks some or all of the entrance to the vagina. It exists in many species, and scientists have no real understanding of its purpose in humans.
Not every woman has the same type of hymen. In some women, the entrance to the vagina is mostly, or completely, unobstructed; in others, a condition called imperforate hymen can block the entire entrance so that not even menstrual blood can escape. There are, of course, variations in between.
What Does the Hymen Have to Do With Virginity?
The presence or absence of the hymen does not say much about a woman's sexual experience. Many women lose their hymen through physical activities such as bike riding, while others maintain their hymens even through early sexual experimentation.
The concept of "popping a girl's cherry" is archaic, as well as medically inaccurate. Even for a woman who still has an intact hymen at the time of her first sexual experience, the hymen usually stretches during penetration, and it may or may not be painful. Sometimes tearing and/or bleeding may occur, but that has to do with the flexibility of the tissue. Every woman's body is different, and so will be her experience with sexual penetration.
Except in societies where a woman's life and social standing may be in danger without this structure that is often misconstrued as physical evidence of purity, there is little to value about the hymen. Nonetheless, plastic surgeons have developed a procedure known as hymenoplasty to recreate the hymen surgically in women who have lost theirs. Although it is somewhat ridiculous for a woman who has had sex to believe that reconstructing her hymen will make her a virgin again, the surgery can be useful for women whose lives might be in danger without it.
Interestingly, some countries consider hymenoplasty to be a form of female genital mutilation, and it is occasionally outlawed under statutes designed to protect young women from this type of violation.