What are the Changes of Adolescence and Puberty The period of transition from childhood to adulthood is called adolescence. The boys and girls passing through this period are called adolescents. The World Health Organization (WHO) defines adolescence as the period of life between 10 and 19 years of age. Adolescence is characterized by changes like development of breasts in … [Read more...] about What are the Changes of Adolescence and Puberty