The human hair has a diameter of about 50 microns, which is also the height of the battery researchers at Rice University have made. After experimenting with larger structures, as proof of concept, the team was able to create a hybrid lithium-ion energy storage device. Part battery and part supercapacitor, the whole thing is built inside of a single nanowire just 150nm wide. Of course something so small cannot compete with the larger batteries we are used to working with, but the devices do show good capacity and can be made as long and as wide as temperature permits. Unfortunately, the current materials only withstand 20 charge-discharge cycles before degrading, but with optimization that could easily improve.