Scientists from the Massachusetts Institute of Technology, US, have made a tiny battery that is as thin as a human hair. This battery is small enough to power robots that are no bigger than the period at the end of this sentence. The battery uses zinc (锌) and oxygen to produce energy. Because it’s so small, it could help tiny robots enter the body to deliver medicine or go into pipelines to find leaks. Previously, these robots needed sunlight or lasers to work, which limited where they could go. This new battery lets them work without needing external power. Currently, these batteries are attached to the robots by wires, but in the future, scientists hope to build the batteries into the robots.