the fly's eye

One familiar illustration in high school science and biology textbooks was that of the eye of the common housefly. The fly's eye has many facets, multiple lenses that offer visual data with high accuity from many directions at once. This works as a great defense because no matter from what direction that flyswatter or frog's tongue comes from, the fly sees it coming and knows it's time to go. What amazing optics on such a small scale!