your body's going through a strange and magical process called "puberty".
Puberty (say: pyoo-ber-tee) is the name for the time when your body begins to develop and change as you move from kid to adult. We're talking about stuff like girls developing breasts and boys starting to look more like men. During puberty, your body will grow faster than at any other time in your life, except for when you were a baby.
It helps to know about the changes that puberty causes before they happen. That way, you know what to expect. It's also important to remember that everybody goes through these changes. No matter where you live, whether you're a boy or a girl, whether you like vanilla or double-fudge-chunk ice cream, you will experience them. No two people are exactly alike, but one thing everyone has in common is that we all go through puberty.
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You can read more about it at this
link.