A whole series of events happens in order for us to see something. First, light must reflect off an object. The light travels through the clear cornea of the eye, and then the lens, which focuses the light onto the retina (the sensory tissue lining the back of the eye). In the retina, cells called rods detect light (they are photoreceptors) and cones detect colors. The rods and cones convert light rays into electrical impulses that are relayed to the brain along the optic nerve. The brain interprets the signals from the eyes and we then "see" what we are looking at.