Bifocal glasses allow wearers to focus on both far and near objects by looking through different parts of the lens. It's commonly said that Benjamin Franklin invented these lenses, but they have actually been around for millions of years. In the streams of North America, the nightmarish larva of the sunburst diving beetle hunts with a pair of natural bifocal lenses.
The beetle relies on its keen eyesight to stalk other insect larvae amid often murky streams. It sees the world through no less than six pairs of eyes and in 2006, Elke Buschbeck discovered that each of these has at least two retinas. One of her students Annette Stowasser has focused on the front pair, and shown that they are unlike any other in the animal kingdom.