At this very moment, your eyes and brain are performing an astounding series of coordinated operations.

Light rays from the screen are hitting your retina, the sheet of light-sensitive cells that lines the back wall of each of your eyes. Those cells, in turn, are converting light into electrical pulses that can be decoded by your brain.

The electrical messages travel down the optic nerve to your thalamus, a relay center for sensory information in the middle of the brain, and from the thalamus to the visual cortex at the back of your head. In the visual cortex, the message jumps from one layer of tissue to the next, allowing you to determine the shape and color and movement of the thing