In a conventional lithium-ion battery, ions moving inside the medium power electrons through an external circuit. In an ingenious reversal of this idea, an “electron battery” sees electrons moving internally while ions are pushed through an external circuit. Liangbing Hu of the University of Maryland in College Park and colleagues have made a prototype with a lithium-anode and vanadium-oxide cathode immersed in an organic electrolyte that stimulates the flow of calcium ions inside living cells derived from human embryonic kidney cells. Biocompatibility was achieved by using Kentucky bluegrass stems soaked in salt solution as ionic cables to connect to the cells. The drifting sodium ions then generate an electric field that releases calcium ions, demonstrating a novel electro-biomedical technology with potential applications including nerve and muscle stimulation.