Based on the results of an adolescent girl’s treatment, the author discusses a major discovery made at the time of adolescence, i.e. the discovery of femininity as such, unknown until then to the subject, whether boy or girl. This “ femininity as such ” is construed by the subject as separate from the sexual being he considered himself as a child. Sexuality rests on phallic primacy which limits relations with others. At puberty, the adolescent will refuse this phallic primacy as a regulating agent of ifs relationship with the outside world, as a limit to sexuality, as a boundary to enjoyment. This “ beyond ” of the phallic dimension, femininity as such, which is a type of enjoyment not fully marked by the phallic limit, must pass through unconscious logic, to allow the emergence of an heterosexual love relationship. The encounter with THE difference, one which embodies all differences, is difficult for adolescents. This detour through femininity, which is a necessary disruption, can also be the cause of serious social and psychic disruptions in adolescents.