Benjamin Franklin is credited with inventing bifocal glasses. These allow wearers to focus on both far and near objects by looking through different parts of the lens. But such lenses have been around for millions of years, on the nightmarish face of the sunburst diving beetle. The beetle’s larva has six pairs of eyes, and the front set is unique in the animal kingdom. Each one has one lens and two retinas, one sitting behind and slightly below the other. The lens manages to focus sharp images onto both of them, so the beetle can see near and far objects at the same time, with equal sharpness. Its bifocal lens gives it two eyes for the price of one.

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