Child development theories and data gathering -- Principles of growth and development -- Prenatal development -- Infancy : birth to twelve months -- Toddlerhood : twelve to twenty-four months -- Early childhood : three-, four-, and five-year-olds -- Early childhood : six-, seven-, and eight-year-olds -- Middle childhood : nine-, ten-, eleven-, and twelve-year-olds -- Adolescence : thirteen- to nineteen-year olds -- When and where to seek help