For mouthless, lungless bacteria, breathing is a bit more complicated than it is for humans. We inhale oxygen and exhale carbon dioxide; Geobacter — a ubiquitous, groundwater-dwelling genus of bacteria — swallow up organic waste and "exhale" electrons, generating a tiny electric current in the process. Those waste electrons always need somewhere to go (usually into a plentiful underground mineral like iron oxide), and Geobacter have an unconventional tool to make sure they get there. "Geobacter breathe through what is essentially a giant snorkel, hundreds of times their size," That "snorkel" is called a nanowire. Though these tiny, conductive filaments...