The dream of a lower-carbon energy grid means somehow storing renewable power generated on windy or sunny days until it is needed. Current batteries can't do it cheaply. In 2011, Stanford researchers announced they had used nanoparticles of a copper compound to develop a battery technology so efficient and inexpensive it could be used for batteries big enough for large-scale energy storage. The material depends on particles a mere 100 atoms wide—an example of how Stanford's growing strength in nanoscale science and engineering supports environmental problem solving.