Pour yourself a glass of water and take a look at it. This water contains an abundant source of fuel, hydrogen. Hydrogen burns clean unlike petrol-based energy products. Sound too good to be true? Scientists in Japan successfully split water into hydrogen and oxygen using light and meticulously designed catalysts, and they did so at the maximum efficiency meaning there was almost no loss and undesired side reactions. This latest breakthrough in solar hydrogen production makes the likelihood of scalable, economically viable hydrogen production more than likely, paving the way for humanity to make the switch to clean energy.