You press a button and — click — the camera freezes a moment forever. How does it catch light and turn it into a picture you can keep?

Inside every camera is a dark box — like a tiny room with all the curtains closed. Light can't get in unless you let it. When you press the button, a little door called the shutter snaps open for a split second, and light rushes through the lens at the front.

The lens is a curved piece of glass that bends the light rays, focusing them into a sharp image — like how a magnifying glass focuses sunlight into a bright dot. All the light bouncing off the tree, the dog, your friend's face, gets bent and aimed at one spot inside the camera.

At the back of the camera sits the sensor — a rectangle covered in millions of tiny light-catching squares called pixels. Each pixel is like a miniature cup waiting to catch light. When the shutter opens, light floods in and fills those cups.

Here's the magic part: each pixel measures how much light it caught and what color that light was — red, green, or blue. Bright light fills the cup high; dim light barely fills it. A pixel in the shadow of the tree catches almost no light. A pixel pointed at the sun catches tons.

The sensor records all those measurements — millions of them, one for every pixel — and saves them as numbers. Bright red might be "255, 0, 0." Dark blue might be "0, 0, 50." The camera now has a giant list of tiny colored dots.

When you look at the photo later, your screen or printer reads those numbers and lights up dots in exactly the same pattern. The top-left pixel was bright green, so the screen makes that spot bright green. The middle pixel was dark, so that spot stays dark. Dot by dot, the whole picture reappears.

That's the whole trick: catch light for a fraction of a second, measure it in millions of places at once, remember the pattern, and paint it back later. Every photo is just a really detailed map of where the light was — and now you have it forever.