We all have one, but how much do we know about them? Dr Karl has put together a few bellybutton factoids to broaden our horizons on the humble navel.

Bellybutton names
Navel-gazing
Bellybutton Scar
Placenta and umbilical cord
Umbilical cord survives internally after birth
Bellybutton shapes
Literature and bellybutton lint
Cancer and the bellybutton
Adam and bellybutton
Belly to breast
Innie vs outies
Drier lint is a canary
Umbilical Cord and Barber's pole
Hair track directs joeys
Bellybutton cleaners
Green bellybutton lint
Animals and bellybuttons
Bellybutton referred pleasure and pain