Photocatalysts absorb energy from light to make a chemical reaction happen. The best known photocatalyst is perhaps chlorophyll, the green pigment in plants that helps turn sunlight into carbohydrates. While carbohydrates may be falling out of favor, photocatalysis is garnering more attention than ever. In a photocatalytic process, light falls on a photocatalyst, increases the energy of its electrons and causes them to break their bonds and move freely through the catalyst. These "excited" electrons then react with the raw materials of a chemical reaction to produce desired products. A top priority in the field of alternate energy research is using photocatalysts to convert solar energy to fuel, a process called "solar-to-fuel production."