A new type of solar cell may one day prove so inexpensive and flexible, it could be used to turn your clothes into portable power sources--keeping you warm or cool, or charging your phone. Materials scientist Paul Alivisatos and colleagues at the University of California, Berkeley, mixed P3HT, a plastic that conducts electricity, with nanorods made from cadmium selenide, a semiconductor material. This mixture was then "spin-cast" onto a glass base, a process similar to swirling a wineglass so that the wine spreads into a thin film. This film was then sandwiched between two conducting layers (one transparent, to admit sunlight) that acted as electrodes. Light striking the middle layer generated an electric current as electrons flowed along the nanorods. The result: a hybrid nanorod-polymer solar cell about one-thousandth as wide as a human hair. The cells could theoretically be spin-cast onto almost any material, including fabric, and since they're based on plastic, the cells withstand bending. Plastic is cheap, too, so the cells could be very cost-effective.