eye]]Eyes are organs of vision that detect light.Different kinds of light-sensitive organs are found in a variety of animals. The simplest eyes do nothing but detect whether the surroundings are light or dark, while more complex eyes can distinguish shapes and colors. The visual fields of some such complex eyes largely overlap, to allow better depth perception (binocular vision), as in humans; and others are placed so as to minimize the overlap, such as in rabbits and chameleons. of a dragonfly.]] In the human eye, light enters the pupil and is focused on to the retina by the lens. Light-sensitive nerve cells called rods (for brightness) and cones (for color) react to the light. They interact with each other and send messages to the brain that indicate brightness, color, and contour. The first proto-eyes evolved among animals 540 million years ago. Almost all animals have eyes, or descend from animals that did. Varieties In