Nipples: Wikipedia says: "In its most general form, a nipple is a structure from which a fluid emanates. More specifically, it is the projection on the breasts or udder of a mammal by which breast milk is delivered to a mother's young. In this sense, it is often called a teat, especially when referring to non-humans, and the medical term used to refer to it is papilla. The rubber mouthpiece of a baby bottle or pacifier may also be referred to as a "nipple" or a "teat". In many cultures, female nipples are considered an erogenous zone and it is considered a public indecency to uncover them in public."
Screw that. Nipples are what many consider to be the best part of the breast, the most sensitive part and the part that if often the most unique between girls. From puffy nipples to innies, no two nipples are exactly the same, even on the same girl. Nipples are fun to play with, fun to diddle, and sometimes used as targets for cumshots.