This chapter examines the complex and dynamic process of human development across the lifespan, from conception to old age. Students will explore the physical, cognitive, social, and emotional changes that occur during different developmental stages, such as infancy, childhood, adolescence, and adulthood. They will also delve into the influential theories of child development, the role of nature and nurture, and the implications of developmental milestones for learning, relationships, and overall well-being.