Nipple
The nipple is a raised and very sensible region within the areola (the darker skin portion) in female and male breasts. When stimulated they come out and become harder. Nipple area is an erogenous zone which can also bring to climax (nipple orgasm). There are no big differences from female and male nipples (beside maybe being more or less hairy and the fact that female nipples get sexualised and therefore censured most of the time).