Nobody wants a laptop computer that stops working when a cloud passes by. Storing sunlight as fuel that can be later used to drive fuel cells requires new materials. Scientists demonstrated such a material. They combined two oxides on the atomic scale. The interface between the oxide materials, one containing strontium and titanium (SrTiO3) and one containing lanthanum and chromium (LaCrO3), absorbs visible light, producing electrons and holes that might be useful for catalyzing reactions, such as producing hydrogen fuel. However, if there is nothing to pull those electrons and holes apart, they will quickly annihilate one another without doing anything useful. By carefully synthesizing this material as a series of alternating layers, the international team created a built-in electric field that could help separate the excited electrons and holes and improve the material’s performance as a catalyst.