When we are talking about gay sex, the bottom is the passive part in anal intercourse, is the man who is penetrated anally with the other man’s penis. Depending on the role chosen for sex, gays define themselves as top, bottom or versatile, being the latter ones those who play both roles. The adopted role can be fixed forever, although it can also change with time and circumstances. It is not very clear what are the determinants of the role that each one acquires, but the different consideration that tops had for a long time regarding the bottoms may have some relation, in this sense during the Roman Empire the homosexual behavior of the men did not suppose any problem as long as the active role was adopted, while the bottom role was rejected both in penetration and fellatio, because it was related to women. It is also true that the fear of pain that may cause penetration can be a barrier to adopt the bottom role, a fact that may explain that versatility increases with age and experience. Anatomically the body of all men is prepared to feel pleasure being penetrated.