Blood Vessels of the Eye reveals to visitors the tiny blood vessels that carry nourishment to the retina. Even though these vessels are always in our field of vision, we normally don’t see them because the brain, coupled with fatigue of the eye’s receptor cells, eliminates them from view. In this exhibit, visitors press a small penlight against their closed eye lid and move it around. Any light entering the eye must pass through the blood vessels to reach the retina, casting a shadow on everything we see. If the penlight continues moving, the eye can’t adapt to the image, and dark reddish lines (like tree branches) will appear which are actually the shadows of the eye's blood vessels.