Dear kiki8888,

It can take up to 20 years of age for all the changes that happen during puberty to take place.

Puberty doesn't happen all at once — it happens in stages. So a girl or guy may show some signs of puberty at an early age (like breasts beginning to grow or a voice that's starting to crack), but may not show other signs of puberty until she or he is much older (like getting a period or growing facial hair).