There are 8 stages of life, each defined by a developmental task. The 4 stages of infancy and childhood are: infancy (birth-1 year, develop trust), early childhood (1-3 years, develop autonomy), middle childhood (4-6 years, develop responsibility), and late childhood (7-12 years, develop interest in activities). Adolescence begins with puberty between ages 12-18 and involves physical and emotional changes. Adulthood has stages including young adulthood (19-40 years) where the tasks are to develop relationships, independence, career, and contribute to society. Marriage requires commitment, communication, maturity, shared values to resolve conflicts.