Here's what your eye would look like if you could see into it from the side. the iris is the coloured part. The black bit in the middle, the pupil, is really a hole that lets light through. It gets bigger or smaller to let more or less light in.

The lens is like a magnifying glass, focusing the light. It's really clever because it can change shape to focus light from things nearby or far away.

The image of what you see falls on the retina at the back of your eye. Actually, it's upside down, but your brain reverses this so that you 'see' things the right way up.

In some people, the lens can't make the image fall exactly on the retina so they're either short or long-sighted. They need to wear glasses or contact lenses, which put another lens in front of their own to make the image fall in the right place.

Try to look after your eyesight. Get an optician to test your eyes every year or so, to make sure you're seeing clearly.

Eyes are soft and squishy. they can get damaged easily if they get hit. Protect your eyes with special goggles if you are doing something which creates dust or flying objects, such as helping with DIY or cutting grass.