This chapter describes the stages of pediatric life. Children go through distinct periods of development as they move from infants to young adults. Stages of pediatric life are used to broadly outline key periods in the human development timeline. During each stage growth and development occur in the primary developmental domains including physical, intellectual, language and social-emotional. This chapter covers the prenatal pediatrics, fetal growth and development, the neonate, respiratory system, circulatory system, gastrointestinal (GI) system, immune system, skin, neurologic system, sensory development, immediate post birth care, assessment of gestational age, physical examination of the newborn, thermal regulation of newborn, breastfeeding and lactation management, to ensure safety, prevent injury and infection, identification and early registration, to identify actual or potential problems and immediate action, the normal infant, the toddler, general characteristics of toddler, overview of the growth and development, cognitive development, physical growth and development, language development, social development, behavior, physical development and role of parent, needs of the toddler, injury prevention, injuries and accidents in toddlers, safe play, preschool child, overview of the growth and development, role of parent in development, special problems of preschool child, promoting optimal health of preschool child, the school child, overview of emotional development in school child, the school child, his family and friends, health problems during school-age, adolescence, and changes during adolescence.