Shewanella oneidensis produce outer membrane extensions that are thought to function as nanowires that transport respiratory electrons to electron acceptors outside the cell. Subramanian et al. have developed a system in which S. oneidensis MR-1 forms outer membrane extensions on an electron microscopy grid inside a perfusion flow imaging platform. Monitoring the same extensions in this chamber with live fluorescence light microscopy followed by electron cryotomography revealed that these are chains of interconnected outer membrane vesicles with electron-dense particles on the interior and exterior. Comparing wild-type S. oneidensis MR-1 with S. oneidensis MR-1 null for cytochrome genes revealed that the electron-dense particles in wild-type S. oneidensis MR-1 are cytochromes. Based on the distance between cytochromes, the authors proposed that in these nanowires, electrons are transported by hopping between, and by the physical diffusion of, cytochromes.