Developmental Psychology is the scientific study of how and why human beings change over the course of their life. It focuses on various stages of development, from infancy through old age, examining physical, cognitive, social, and emotional growth. Key figures in this field include Jean Piaget and Erik Erikson, who contributed significantly to our understanding of developmental stages. This branch of psychology explores how individuals develop skills, personality, and behavior in response to their environment. It also investigates the impact of factors such as culture, family, and education on development, providing insights that can help in areas like education and mental health.