Where growing happens
Your bones don't grow longer all over, like a balloon blowing up. They grow at special spots near their ends, called growth plates.
A growth plate is a thin layer of cartilage, the bendy stuff in your nose. Long bones, like your thigh bone, shin bone and arm bones, usually have one near each end.
On an X-ray, a special picture of bones, growth plates show up as dark lines near the ends of a kid's bones. Grown-ups don't have those lines.
How a bone gets longer
In a growth plate, cartilage cells keep making new cells, stacked up like piles of coins. The new cartilage pushes the end of the bone a tiny bit farther away.
Then, on the side closer to the middle of the bone, the older cartilage turns into hard bone. So the bone gets a tiny bit longer.
This happens again and again, day after day. You can't feel it, but it adds up. That's how you outgrow your shoes and pants!
You grew fastest as a baby: about 10 inches, or 25 centimeters, in your first year! After that, most kids grow about 2 inches a year.
When growth plates close
Growth plates don't stay forever. Around the end of the teen years, the cartilage in them turns all the way into bone. Doctors say the plates have closed.
After that, bones can't get any longer. That's why grown-ups stop getting taller.
Different plates close at different times, and every person has their own schedule. Some kids grow early and some grow later. Both are normal.
Help your bones grow
Sleep. Your body makes a growing helper called growth hormone, and it sends out lots of it while you're deeply asleep.
Food. Growing bones need calcium, from foods like milk, yogurt, cheese, beans and leafy greens. They need vitamin D, from eggs, fish and milk with added vitamin D. They need protein too, from foods like eggs, beans, fish and meat.
Play. Running, jumping and climbing tell your bones to get thicker and stronger.
Kids and teens build most of the bone they'll ever have. So the healthy habits you have now help your bones for your whole life.
Always rebuilding
Even after you stop growing, your bones keep changing. Builder cells add new bone, and cleaner cells take away old bone, all the time.
Bit by bit, they replace your whole skeleton about every 10 years. Bones are never really finished!
This is also how a broken bone heals. Builder cells make new bone to fill the gap and join the pieces back together.