Developmental psychology is the branch of psychology and the scientific study of how people grow and change over the course of a lifetime. Originally concerned with infants and children it expanded to include adolescence, adult development, ageing, and the entire lifespan. Beginning with Sigmund Freud (1856-1939) and Jean Piaget (1896-1980), the early focus of developmental psychology was on the maturation of children. Within the last three decades, researchers who study human development have expanded their focus to examine change across a broad range of topics including psycho-physiological processes; cognitive development involving areas such as problem solving, moral and conceptual understanding; language acquisition; social, personality, emotional development, self-concept and identity formation.The scientific study of human growth and development is important not only to psychology, but also to biology, sociology, anthropology, education, history and health care. Most important, however, are its practical applications. By better understanding how and why people change and grow, the knowledge can be applied to help people to reach their full potential.