The laws of successive social maturation of a growing person are described using adolescence as an example. Deep analysis of the stage-by-stage development of an adolescent is presented. This development is considered through the peculiar characteristics of self-consciousness in the different manifestations thereof - self-evaluation, personality reflexion, requirements on oneself and on others, motives of activity, ideals, interests of the children of different age groups (10-11, 12-13 and 14-15).