This article aims to present Daniel Stern's concept of the development of the self in the relationship with the caregiver and to describe how the core aspects of the self manifest themselves in the psychotherapy process. Stern's research on the relationship between mother and child inspired him to analyze in detail what happens moment by moment in the therapist-patient relationship. In the paper, the processes of the emergence of the self will be described. These processes involve the development of the young child's self in the relationship with the caregiver and become the basis for experiencing oneself in a relationship with another, including the therapeutic relationship. Awareness of self development is of particular importance in psychotherapy. The "coming into being" of the patient's self in the relationship with the therapist involves a continuation and evolvement of experiencing the self that emerged in the first months of the child's life. The second part of the paper describes the phenomenon of change in the psychotherapy process. The article emphasizes a "moment-by-moment" relationship with the caregiver that contributes to forming the child's self and the 'realization' of this intersubjective pattern in the therapeutic relationship.