Everybody knows that there are two kinds of nipple.
The first kind of nipple looks like a nipple, or, perhaps, a kitten's nose. Gentle but perky, with a hint of moist juiciness, it is usually attached to what family newspaper editors like David Dinsmore like to call hooters, funbags, or chumbawombas. It can also be seen on a daily basis through pretty much anything worn by Rihanna or Beyonce.
The second kind of nipple, conversely, looks like something you might find stuck to your shoe i.e chewing gum. Often the result of extreme breastfeeding, which in the UK means breastfeeding for more than three days, it could also (apparently) be mistaken for an attack of ringworm, or a scary witch's teat, which is why you never see it featured in newspapers, magazines, campaign billboards, or on the catwalks at New York Fashion Show.