Puberty

Puberty is the time when a child's body changes into an adult body. It usually begins between ages 8 and 13 for girls and between ages 9 and 14 for boys. The whole process takes several years. By the end, a person is able to have children of their own. Puberty happens to every healthy person, though the timing is different for everyone.

Puberty is controlled by chemicals in the body called hormones. Hormones are made by small organs called glands. A gland in the brain, the pituitary gland, sends signals to other glands. Those glands then make the hormones that drive puberty. The two main ones are estrogen, which mostly shapes female changes, and testosterone, which mostly shapes male changes. Both bodies make some of each.

Some changes happen to almost everyone. Kids grow taller, sometimes very fast. A "growth spurt" can add three or four inches in a single year. Hair starts to grow under the arms and in new places on the body. Skin makes more oil, which can lead to pimples called acne. Sweat glands turn on, so body odor becomes a thing. Feet often grow first, which is why many tweens go through a clown-shoe phase before the rest of them catches up.

Other changes are different for boys and girls. In girls, hips widen, breasts develop, and menstrual periods begin. In boys, the voice gets deeper, facial hair starts to grow, and shoulders broaden. Boys' voices can crack during this time because the voice box, called the larynx, is growing quickly and the muscles inside it are still learning the new size.

The brain changes too, and this part is less obvious from the outside. The parts that handle strong feelings develop early in puberty. The parts that handle careful planning and self-control keep developing into the mid-twenties. Scientists think this gap is one reason teenagers often feel emotions strongly and sometimes take big risks. The brain is still under construction.

Puberty can feel strange, exciting, or uncomfortable, sometimes all in the same week. Starting earlier than friends, or later, is normal. Doctors used to think the average age of puberty stayed about the same over time. New studies show it has been starting a little earlier in recent decades, and researchers are still trying to figure out why.