Tiny feelers everywhere
Your skin is packed with nerve endings. They're the tips of nerves, like the ends of very long, thin wires that run to your spinal cord and brain.
Different nerve endings feel different things. Some feel a light tickle, like a feather. Some feel a firm press, like a hug.
Some feel buzzing, like a phone vibrating in your hand. Some feel your skin stretch when you bend your fingers.
Others feel heat, cold, itch and pain. Together they paint a picture of the world for your brain.
Super-sensitive spots
Some places have far more nerve endings than others. Your fingertips, lips and tongue are some of the most sensitive parts of your whole body.
Your back has fewer, spread far apart. Try this with a friend: with their eyes closed, gently touch their back with one pencil eraser, or two close together. It's hard for them to tell one from two! On a fingertip, it's easy.
That's why you feel for things with your fingertips in a dark room, and why babies explore toys with their lips and mouths.
Racing to the brain
When a nerve ending feels something, it sends a tiny electrical message along a nerve, up your spinal cord to your brain.
Touch messages zoom along at up to about 150 miles an hour. That's faster than a car on the highway!
Your brain then works out what it is: soft cat fur, a cold ice cube or a bug landing on your arm.
Some pain messages travel more slowly. That's why when you stub your toe, you feel the bump first and the ache a moment later.
Pain, the helpful alarm
Pain doesn't feel good, but it's a helper. It works like a smoke alarm for your body.
When you touch something too hot, pain nerves warn you so fast that your hand jumps back before you even think about it. That quick move is called a reflex (REE-flex).
Pain also reminds you to rest a sore ankle or take care of a cut, so it can heal.
If something hurts a lot, or keeps hurting, tell a grown-up.
Hot, cold and itchy
Some nerve endings notice warmth, and others notice cold. Together they tell you when bath water is just right.
Itch has its own special nerves. An itch is your skin's way of saying something is bugging it, like a scratchy tag, dry skin or a bug bite.
Scratching can feel good for a moment, but it can also make skin sore. A cool cloth can help instead.
Why you can't tickle yourself
Your brain knows exactly when and where your own fingers will touch you. It's ready for the touch, so it isn't a surprise.
When someone else tickles you, your brain can't guess what's coming next, so it feels ticklish.