Ancient oceanic hydrothermal vents may have been one of the earliest habitable environments on Earth. Dodd et al. examined ferruginous sedimentary rock from the Nuvvuagittuq supracrustal belt (NSB) in Quebec, Canada, for the presence of microfossils that are suggestive of early microbial life. The NSB is a fragment of primitive oceanic crust with evidence of hydrothermal vent activity that is between 3,774 and 3,751 million years (possibly up to 4,280 million years) old. Remarkably, the authors observed distinctive filament and tube microstructures in NSB rock samples. These structures were similar in morphology to filamentous iron-oxidizing bacteria that are found in modern hydrothermal vents. The samples also contained preserved minerals and carbonaceous material in rosettes and granules, which may have been formed by the oxidation of biomass. This is suggestive of metabolic processes that are inherent in life. These microfossils are thus far the oldest evidence of life on Earth.