The first comprehensive lifespan view was developed by Erik Erikson. It is called the Erikson's stages of psychosocial development which identifies eight stages where a developing individual should be able to go through from infancy to adulthood. These stages are infancy (0 to 23 months), early childhood (2 to 4 years), preschool years (4 to 5 years), school age (5 to 12 years), adolescence (13 to 19 years), early adulthood (20 to 39 years), adulthood (40 to 64 years) and maturity (65 to death). In each stage, specific values, psychosocial crisis, significant relationship and existential question are being specified by Erikson.