Researchers have created a coating that reflects almost no light, thanks to a refractive index close to that of air. A material's index of refraction refers to the speed of light in that substance, which in turn governs how much light bends when it passes into the substance. The new material consists of angled nanorods laid on top of a transparent semiconductor wafer. By stacking five layers of nanorods, each one less porous than the one below it, the researchers could vary the coating's refractive index in a series of steps, going from 2.03 at the bottom (closely matching the wafer) to 1.05 at the top (compared with 1.0 for air). Total reflection dropped to as little as 0.1 percent, note E. Fred Schubert and his group at Rensselaer Polytechnic Institute in the March Nature Photonics. The coating should prove useful in boosting the efficiency of LEDs and solar cells.