Leaves – the kind that grow on trees – create energy from sunlight and water through the process of photosynthesis. For over a decade, scientists have been kicking around the idea of creating an "artificial leaf." Such a device would use sunlight to split water into hydrogen and oxygen, which could then be stored in a fuel cell and used to create electricity. A functioning artificial leaf has been created before, but was impractical due to the fact that it was made from expensive materials, and was highly unstable. Now, however, scientists are reporting that they have created a cost-effective, stable artificial leaf.