Puberty is the period of sexual maturation where the body goes through physical and biological changes to become capable of reproduction. It is triggered by hormonal changes that cause development of secondary sex characteristics. Girls typically start puberty between ages 8-13, while boys start between ages 9-14. Puberty results in growth of breasts and pubic hair in girls and a deeper voice and growth of pubic hair and testes in boys. Both experience mood swings and skin changes during the process.