Slideshow: The Stages of Puberty

Puberty: It's Not One Size Fits All

Puberty's changes start when the brain triggers the production of sex hormones. Although physical changes follow a predictable pattern, every child develops at his or her own pace. Puberty usually begins for girls before boys. For most girls, puberty begins around age 11. For boys, puberty starts from 10 to 14. The average age is 12.

Budding Breasts Can Signal Puberty

Breast growth is usually the first sign of puberty girls will notice. First, small lumps form behind the nipples. They can be sore, but the pain goes away as breasts grow and change shape over the next few years. As they grow, it’s not unusual for one breast to develop more slowly than the other. Boys also may have some swelling on their chest but it tends to go away within a year or two.

Boys: Genital Changes

The first sign of puberty in boys is subtle -- an increase in testicle size. About a year later, the penis and scrotum start to grow. Semen can be released during an erection when he is awake or when he is asleep.

Hair Growth in Puberty

After breasts and testicles start growing, body hair will start to grow in and become thicker.  For both boys and girls, new hair will start growing in the armpits and pubic area around the genitals. Arm and leg hair gets thicker. Boys also may start developing chest and facial hair.

Acne: An Early Sign of Puberty

Mild acne may be normal in early puberty. Puberty's high hormone levels can trigger acne outbreaks. During puberty, the oil glands are more active and your child will probably sweat more. Keeping the face and body clean can help, but if acne is a concern, talk to a doctor. Medications may help.

Later Stages of Puberty for Girls

About a year after puberty begins, girls have a growth spurt. A girl will get taller and start to get wider hips and fuller breasts. Some curve-related fat will appear on her stomach, buttocks, and legs. Girls usually reach adult height by their mid- to late teens.

Growth Spurts: From Boys to Men

The peak growth spurt for boys happens later than it does for girls. It occurs around six months after pubic hair development. When it does, your son's shoulders will become fuller and broader, and he'll grow taller, too. His face shape will look less round and more adult-like. Depending on when puberty starts, he may not reach his adult height until his late teens or even early 20s.

The First Period: Puberty's Ending

A girl usually gets her first period between 10 and 16 years old (about 2 to 2 1/2 years after she starts puberty.) Menstruation is a sign that she's physically an adult and is able to get pregnant. You may want to talk to your doctor if your daughter doesn’t get her first period by the time she's 16.

Puberty Causes Cracking, Deeper Voices

Toward the end of puberty, your son's voice may start cracking. This is normal, and will stop after a few months. When it does, his voice will sound deeper. Voice changes are caused by testosterone, a hormone released in boys during puberty. It causes the vocal cords to get thicker and longer and his larynx to grow bigger. This is his "Adam’s apple."

Growing Up Too Fast: Early Puberty

Some kids become sexually mature at a very early age. Early or precocious puberty is when a child reaches a physical or hormonal milestone -- breast, testes, or pubic hair growth -- before age 6 to 8 in girls or 9 in boys. Early puberty is linked with obesity in girls. Early puberty rarely is due to hormone exposure or a problem with the thyroid, ovaries, or brain. Talk to your doctor if you're concerned.

When To Call The Doctor

Keep track of your child's bodily changes in a way that respects his or her desire for privacy. Call the doctor if:

• Puberty signs appear in a girl before age 6-8 or in a boy before age 9
• Puberty changes aren't seen in a girl by age 13 or in a boy by age 14
• Puberty changes do not follow the typical pattern of development