A conceptual model of appearance and development of the inner world in man's ontogenesis is offered. Co-being of an adult and an infant, of an infant and other people forms the starting ontological basis of man's "Self". Behind the dynamics of the co-being and development of individual capacities there are processes of identification of the child with others and processes of his individuation, separation from others. Intertwined work of mechanisms of imitation and reflectivity underlies the process of development of the inner world. Particular forms and contents of Self at different ontogenetical stages are considered.