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Changes During Puberty for Boys and Girls

What is puberty? Growing up. Everyone goes through the same process. Whether you start at age 9 or at age 15, it’s all “normal.’’You are still you inside. Your body and feelings are changing at their own pace. Growing up can be a great experience: a time of changing and finding out who you are.

Fully developed females
At 18, you'll pretty much have your adult body.

Developing females
At 15, you'll see less difference between you and your friends.

Undeveloped females
At 12, you may have a young girl's body or begin to look like a woman.



Breasts come in all shapes and sizes. Some girls’ breasts grow early; others grow late. Most girls have one breast that grows faster than the other.

  • Your breasts start growing, first with the nipples and the dark area around them (the areolae).

  • Your feet and hands grow next.

  • Then you’ll gain most of your height and muscle.

  • Underarm and pubic hair appear first as downy fuzz, and later grow thicker and darker.

  • Adipose tissue (fat) gives you a curvier shape; a certain amount of fat is needed for normal periods.

Fully developed males
At 18, you'll see less difference between you and your friends.

Developing males
At 15, you might look like a child or a young man: either one is normal.

Undeveloped males
At 12, you'll probably still have a young boy's body.



An erection is the swelling and stiffening of your penis. Erections don’t only happen in sexualsituations. It’s also normal to get a “hardon’’ just from your pants rubbing against you.

  • Your testicles start to grow. Then your penis grows.

  • Your feet and hands grow next.

  • Your muscle may double and you gain most of your height.

  • Underarm hair, pubic hair, and facial hair appear first as fuzz, and later grow thicker and darker.

  • Your breast tissue may grow a bit and then shrink.

  • Your voice deepens.

Online Medical Reviewer: Bass, Pat F. III, MD, MPH
Online Medical Reviewer: MMI board-certified, academically affiliated clinician
Date Last Reviewed: 3/3/2014
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