Theories of Human Development explore how individuals grow and change throughout their lives. Key theories include Erik Erikson's psychosocial development, which outlines eight stages from infancy to adulthood, each characterized by a specific conflict. Another important theory is Jean Piaget's cognitive development, which describes how children develop thinking skills in four stages, from sensory-motor to formal operations. Additionally, Lev Vygotsky's sociocultural theory emphasizes the role of social interaction and culture in learning. Sigmund Freud's psychosexual stages focus on how early experiences shape personality. Together, these theories provide a framework for understanding the complex processes of human growth and development.