Photovoltaics, otherwise known as solar cells, are an important source of energy around the world, converting solar radiation into electricity which we use every day to power our lights, computers, and appliances. But even the most advanced solar cells can only use a fraction of the sun's energy What if we could use the unused solar energy to also produce fuel? Matt Shaner, a graduate student in the Lewis Research group at Caltech, shows us a demo of an intriguing new technique in the production of hydrogen, a promising alternative fuel. Plants convert the sun's energy into sugar through photosynthesis. In this process, hydrogen is produced when the sun's rays hit a piece of silicon, a material often found in photovoltaic cells.