The period of time when children are growing into adults is called adolescence. The early part of adolescence, when bodies change, is called puberty. The changes take place at any time between the ages of 10 and 15. Here are some of them.
• Girls start to menstruate (have periods). Their breasts start to grow bigger, their hips get broader and they grow more body hair.
• boys start making sperm in their testes. They grow facial hair and their voices 'break' or deepen. Their shoulders and chest become broader.
• in old age, bones become more fragile, skin stretches and wrinkles, and hair often goes white and get thinner.
Muscles become weaker and some people cannot hear or see as well as they once could.