The document outlines the five main stages of human development: pre-natal (conception to birth), infancy (birth to 3 years), childhood (3 to 12 years divided into early and later), adolescence (12 to 19 years divided into early and later), and adulthood (beyond 19 years). It then provides more details on the characteristics of infancy, noting it is a time of rapid adjustment and growth from birth to age 3 where development plateaus in preview of later stages.