Two professors at the University of Colorado in Boulder have developed a film embedded with glass spheres that provides a passive cooling effect. Twenty square meters of the material would be enough to keep a room at 20°C in 37°C weather. The real kicker is that it is actually cheap to produce. A thin plastic sheet may soon provide some relief from the intense summer sun. The film, made from transparent plastic embedded with tiny glass spheres, absorbs almost no visible light, yet pulls in heat from any surface it touches. Already, the new material, when combined with a mirrorlike silver film, has been shown to cool whatever it sits on by as much as 10°C. And because it can be made cheaply at high volumes, it could be used to passively cool buildings and electronics such as solar cells, which work more efficiently at lower temperatures.