Using tiny wires and fishnet structures, researchers at the University of California, Berkeley, have found new ways to bend light backward, something that never occurs in nature.

This technology could lead to microscopes able to peer more deeply and clearly into living cells. And the same kind of structures might one day be adapted to bend light in other unnatural ways, creating a Harry Potter-like invisibility cloak. “This is definitely a big step toward that idea,” said Jason Valentine, a graduate student and a lead author of a paper to be published online Wednesday by the journal Nature. But scientists are still far from designing and manufacturing such a cloak.

The work involves materials that have a property known as negative refraction, which means that they essentially bend light backward. Once thought to be pure fantasies, these substances, called metamaterials, have been constructed in recent years, and scientists have shown they can bend long-wavelength microwaves.

Negative refractive materials can in principle lead to fantastical illusions; someone looking down at a fish in a pool of negative refractive liquid would see the fish swimming in the air above.