n the planet’s soils and sediments, there are giant electrical grids made of rocks and microbes.

Throughout the last decade, scientists have shown that bacteria can transfer electrons between one another to produce electric currents. Some of them do so with hair-like extensions called pili, which act as tiny electric wires. Now, we know that some can use iron minerals to transfer electrons instead.

All living things rely on relays of electrons. In our cells, proteins strip electrons from food and pass them along to one another, eventually depositing them onto oxygen. This releases the energy that fuels our existence. In animals and plants, these electron transfer chains are restricted to individual cells. But in bacteria, the chains encompass many cells, even