Fifteen years ago, electric currents were reported from marine sediments and the electron conduits were found to be centimeter-long multicellular Desulfobulbaceae with wires in a common periplasm. These cable bacteria, as they were named, bring electrons from anaerobic sulfide oxidation at depths to oxygen or nitrate reduction at the sediment surface. In doing so, they induce distinct physiochemical gradients influencing the fate of numerous elements, pollutants, and greenhouse gasses. With at least two genera and nine species, they are found worldwide in marine and freshwater sediments. No known, biological electron conduit compares with their wires which also harbor a reversible electrochemical catalyst for oxygen reduction. A key component of the wires seems to be a nickel-sulfur compound. Other bacteria can be attracted to cable bacteria as an electron sink and cable bacteria themselves can be attracted to graphite anodes. The presentation will focus on recent advances and open questions in cable bacteria research.