Black Haired Girl On The Chair With A Navel Tattoo

The navel (clinically known as the umbilicus, also known as the belly button) is a scar on the abdomen, caused when the umbilical cord is removed from a newborn baby. All placental mammals have a navel. It is fairly conspicuous in humans.
In humans, the scar can appear as a depression (often referred to colloquially as an innie) or as a protrusion (outie). Although they can be separated into these two categories, navels actually vary quite widely among people in terms of size, shape, depth/length, and overall appearance. As navels are scars, and not in any way defined by genetics, they can serve as a way of distinguishing between identical twins in the absence of other identifiable marks.