This document provides an overview of key concepts in human development from prenatal stages through adulthood. It discusses four main questions of developmental science: plasticity, individual differences, continuity, and sources of development. The stages of development are divided into ages and domains. The sources of development are explored through nature versus nurture and ecological models. Critical periods and the effects of injury on plasticity are examined. Individual differences are considered in terms of the nature of differences between people and consistency of characteristics across the lifespan. The primary objectives are to compare developmental theories using the four questions, observe child development, and examine adult development through case studies.