Lev Semyonovich Vygotsky was a Russian and Soviet psychologist, best known for his work on psychological development in children and creating the framework known as cultural-historical activity theory. After his early death, his books and research were banned in the Soviet Union until Joseph Stalin's death in 1953, with a first collection of major texts published in 1956.

Developmental psychology is the scientific study of how and why humans grow, change, and adapt across the course of their lives. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, aging, and the entire lifespan. Developmental psychologists aim to explain how thinking, feeling, and behaviors change throughout life. This field examines change across three major dimensions, which are physical development, cognitive development, and social emotional development. Within these three dimensions are a broad range of topics including motor skills, executive functions, moral understanding, language acquisition, social change, personality, emotional development, self-concept, and identity formation.