A research group at the California Institute of Technology is designing an artificial leaf which mimics the energy conversion process of vegetation. This “leaf” consists of a grid of silicon nanowires, each 1,000 times thinner than a hair. Each fiber is coated with a chemical catalyst. When exposed to the sun, a two-step process occurs. First, electricity is produced, as in solar panels. In the second step, the current of electrons splits water molecules into the component atoms of oxygen and hydrogen. The hydrogen gas is then concentrated and stored as a fuel for later use in cars or the large-scale generation of electricity.