How long does puberty last?
Before puberty, there are hardly any differences between girls and boys. Their bodies, faces and voices are similar. The biggest differences are in their external sex organs (the visible genitals) – although they aren’t very developed at this stage.
It is still not clear what actually triggers puberty. Girls start puberty at around age nine. Boys don’t start until they’re around eleven. When puberty begins, the child’s brain sends signals to start the production of sex hormones. At first, these “chemical messengers” are made in the adrenal glands. The hormones then trigger gradual changes in the child’s body. One of these changes is the development of the reproductive glands (gonads). In boys, these are the testicles (commonly called "balls" or "nuts"). In girls, they are the ovaries. Later, the sex hormones are made in the gonads, and then larger amounts are released into the bloodstream.
Puberty ends in stages: Most girls reach sexual maturity by the age of 14; most boys by the age of 16. Girls’ bodies normally stop growing around the age of 16. Boys have usually finished growing by the time they’re 19. But it can take up to the early twenties for the last physical changes to happen. This can even take a little longer in boys.