An eye is the organ that lets you see. Your eyes detect light and send signals to your brain, which turns those signals into images of the world around you. Eyes work like sophisticated cameras: light enters through the pupil (the dark circle in the center), passes through a lens that focuses it, and hits the retina at the back of your eye, which captures the image and sends it to your brain.

Different animals have eyes adapted to their needs. An eagle's eyes can spot a rabbit from a mile away. A cat's eyes work well in near darkness. Some insects have compound eyes made of thousands of tiny lenses. Human eyes can distinguish millions of colors and adjust from bright sunlight to dim candlelight.

The word also means the center of something, like the eye of a storm, which is the calm area at a hurricane's center. A needle's eye is the small hole you thread with string. When someone has an eye for detail, they notice small things others miss. If you keep an eye on your little brother at the playground, you're watching him carefully. And when you see eye to eye with someone, you agree with them completely.

Your eyes reveal a lot about how you're feeling: they widen with surprise, narrow with suspicion, or sparkle with excitement, which is why people say eyes are the windows to the soul.