All of a zebra’s fur, both black and white, grows from follicles that contain melanocyte cells. These cells are present in all animals, and they’re primarily responsible for generating the pigment that gives colour to skin and hair. In both cases, melanocyte cells produce melanin—the pigment—that is outwardly visible. In zebras, chemical messengers determine which melanocytes deliver pigment to which section of fur, thus creating the zebra’s black and white pattern. What’s important about zebras is that their white fur represents an absence of melanin; white is not its own pigment. Since white stripes only exist because pigment is denied, black is understood to be the “default” colour of a zebra.