Self-concept is the abstract idea of an individual held by that person. This article describes six aspects of the self-concept that develop in toddlerhood: (1) self-recognition, (2) self-representation, (3) self-description, (A) self-assertion, (5) self-evaluation, and (6) self-regulation. After a brief historical overview, the theoretical and empirical background and measurement examples are presented for each of these domains of self-concept. Finally, the authors use information about caregivers' influence on the self-concept and the overlap with mastery motivation to suggest applications of this model. The intervention ideas are based on three dimensions of the socializing environment: (1) the provision of inanimate objects, (2) emotional communication, and (3) instrumental interaction.