This document discusses adolescent health and development. It defines adolescence as the period between ages 10-19 according to WHO. Adolescence involves rapid physical, psychological, and social changes as individuals transition from childhood to adulthood. The document outlines the stages of adolescence and changes that occur during puberty like physical growth and sexual maturation. It also discusses common health issues adolescents face like injuries, substance abuse, nutritional problems, and mental health issues. The document emphasizes the importance of adolescent health and the need for prevention strategies like education, screening, and vaccination programs to promote healthy development.