A new kind of lens reaches an unprecedentedly sharp focus by giving up on being perfect. The lens is the first ever to help take visual light images of structures smaller than 100 nanometers, which could make it useful for nanotechnology and probing the insides of cells.

Ordinary lenses, like those used in magnifying glasses, have curved surfaces that bend light to a single point. A small object sitting at that point appears larger and sharply focused, helping myopic readers discern fine print and old-school detectives search for fingerprints. But conventional lenses need to be almost perfect...