Carbon is a fundamental element of life on our planet. Here, swimming bacteria tracked over time (blue) consume organic carbon from a decaying diatom (silver, 0.1 mm long). The association between such primary producers and decomposers presents a microcosm of the complex biological and chemical interactions that occur in seawater. Microscopy, and the ability to turn images into data, allows researchers to make mathematical models for figuring out how microbe-scale activities can impact the carbon cycle and our global ocean.