Microbes -that is, single-celled organisms invisible to the naked eye- thrive in marine environments with concentrations at the surface sometimes exceeding 1 million of cells per millilitre. These high abundances make them fundamental players in the cycling of carbon and other elements, both within the ocean and their exchange with the atmosphere. The activity of these tiny organisms, from viruses, bacteria and archaea to larger eukaryotic protists (microalgae, nanoflagellates and ciliates) and their interactions with dissolved organic matter will, therefore, be also crucial in the response of our planet to global change. Just in front of KAUST, the Red Sea –the hottest and saltiest deep basin in the world– offers us a perfect natural laboratory where to conduct research about how future conditions will shape the microbial landscape of the oceans.