The boss of your body
Your brain sits inside your skull, the hard bone helmet in your head. It is soft and squishy, a bit like firm jelly, and it is wrinkly all over.
A grown-up's brain weighs about 3 pounds, about as heavy as a small melon.
Your brain is in charge of everything you do. Some things you choose, like kicking a ball. Other things happen all by themselves, like your heart beating and your lungs breathing.
Your brain is only a small part of your body, but it uses about one fifth of your body's energy. Thinking is hard work!
Billions of nerve cells
Your brain is made of about 86 billion nerve cells. Scientists call them neurons (NOO-rons). If you counted one every second, it would take you more than 2,000 years.
Neurons pass tiny signals to each other, a bit like a giant game of telephone. Each neuron can link up with thousands of others.
When you learn something new, your neurons make new links. When you practice, those links get stronger. That is why practice makes things easier.
The parts of your brain
The biggest part is the cerebrum (suh-REE-brum). It is split into two halves, a left side and a right side. Here's a twist: the left half mostly runs the right side of your body, and the right half runs the left side.
Each half has four main areas called lobes. The frontal lobe, behind your forehead, helps you think, plan and make choices. The parietal (puh-RYE-uh-tul) lobe, on top, feels touch. The temporal lobe, near your ears, helps you hear and remember. The occipital (ok-SIP-ih-tul) lobe, at the back, helps you see.
Tucked under the back of the cerebrum is the cerebellum (sair-uh-BELL-um). It helps you balance and move smoothly, like when you ride a bike or catch a ball.
The brain stem joins your brain to your spinal cord. It runs the jobs you never have to think about, like breathing, your heartbeat and swallowing.
Sleep, learning and growing
While you sleep, your brain stays busy. It sorts out what you learned that day and saves the important parts as memories.
Kids from about 6 to 12 years old need about 9 to 12 hours of sleep each night. A rested brain pays attention better, remembers more and feels calmer.
Most dreams happen in a part of sleep called REM, when your eyes dart around under your eyelids.
Your brain grows fast when you are little. By about age 6, it is already close to its grown-up size. But it keeps changing and learning your whole life.
Brain myths
Myth: You only use 10 percent of your brain. Truth: You use all of it. Brain scans show that over a day, every part gets put to work.
Myth: People are either left-brained or right-brained. Truth: Both halves work together all the time, for math, art, music and everything else.
Myth: A headache is your brain hurting. Truth: The brain itself has no pain sensors. A headache comes from the parts around it, like muscles and blood vessels.