Vision allows us to see color, motion, form, and shadow. Our brain interprets images so that we understand what we see. In this episode, series host and naturalist Diane Ackerman considers both the biology of vision and the mental processes and perceptions that govern vision. She seeks answers to how the brain makes sense of optical illusions, what the importance of eye placement is in predatory animals, how artists use light and color, and why the sky is blue.