Your belly button, or navel, is a scar where your umbilical cord once was. The tubelike cord connected you to your mother when you were inside her uterus, growing into a baby. It carried oxygen and nourishment to you from the placenta, an organ that develops in the uterus during pregnancy, connecting you to your mother’s blood supply. (It also carried away waste products from your blood.) Once you were born, the umbilical cord was no longer needed, because you began to breathe and eat on your own. The cord was clamped off and cut, and what was left of it withered and dropped off about a week after your birth. Doctors clamp the cord and cut it, leaving a remnant two to three inches long that eventually shrivels up and falls away. Skin grows over the area, and it then becomes the belly button shape you have for life.