This document discusses the meaning and approaches to human development from conception through the lifespan. It defines human development as the pattern of growth and change that begins at conception and continues throughout life. Major principles of development discussed include relatively orderly progression from head to toe (cephalocaudal pattern) and from center of body outward (proximodistal pattern), as well as variability in outcomes and rates of development among individuals. Development involves complex interactions between biological, cognitive, and socioemotional processes. Traditional and lifespan approaches to understanding development across the lifespan are also presented.