The hymen is a thin piece of mucosal tissue that surrounds or partially covers the external vaginal opening. It forms part of the vulva, or external genitalia, and is similar in structure to the vagina.

During puberty, oestrogen causes the hymen to change in appearance and become very elastic. 

The hymen can rip or tear during first penetrative intercourse, which usually results in pain and, sometimes, mild temporary bleeding or spotting. The state of the hymen is not a reliable indicator of virginity , although it continues to be considered so in certain cultures.