Young people do not develop their self and identity in a social vacuum, but in a continuous interactive process involving significant members of their social networks. In this article, we discuss various mechanisms through which interactions in different developmental contexts impact adolescent self and identity formation. Furthermore, we underline that this process is not unidirectional: in fact, the more adolescents achieve a clearer sense of who they are, the more they can exert an active influence in their contexts. In discussing this dynamic process, we will show evidence drawn from longitudinal studies with adolescents. Specifically, we will examine self and identity formation in the family, school, and civic contexts.