Eyes are very complicated. They have a lot of different parts, and all of the parts are important. You might have to explain this to a grown-up so they can understand how eyes work.
Let's start with light. Light bounces off things and some of it goes through the pupils in our eyes. Those are the little black circles.
Then it passes through a lens which bends it and focuses the light on our retina, which is a thin tissue at the back of the eye. Focusing means that light from one part of what we are looking at goes to one place on the retina.
Just like the rest of your body, the retina is made up of tiny cells.
These are too little to see without a microscope. The cells in your retina are special because they make chemicals called dyes. When light hits the dyes, the dyes get bleached out, the chemicals break down. You can see this effect with colored construction paper if you put a piece in a sunny window and cover part of it with something light doesn't go through. After several days or a week, you will see the sunny part has faded. Your eye cells work MUCH faster. Your cells keep track of the dyes, and as they replace the worn out ones, they send a message to your brain about the light that has hit them.
Your brain puts together all the information it gets from all the cells in your retina to figure out what you are seeing. It is a truly amazing process.
