Video narration
How does light entering your eye become a scene you can see? Think of a phone camera: it focuses light onto sensors. Your eye has a similar first job, but its parts do the work in their own way. Light first passes through the cornea, the clear front surface that bends it, then through the pupil, the opening at the center of the eye. The iris changes the pupil's size to control how much light gets in. Next, the lens fine-tunes the focus, directing light onto the retina at the back of your eye. Here, light-sensitive cells turn the light pattern into nerve signals. But reaching the retina isn't seeing. The optic nerve carries those signals to your brain, which interprets them as the scene around you. Your eye focuses light onto the retina; the optic nerve carries its signals to your brain, where they become sight.