As a postdoctoral fellow in the “Diversity of Oceanic Plankton group” (DIPO, Station Biologique de Roscoff), I have focused on the diversity and ecology of marine phytoplanktonic picoeukaryotes. These single cell organisms, 1,000 times smaller than a grain of sand, represent together with cyanobacteria, the smallest entities (around 0.2 – 3 μm) in the ocean that can photosynthesize. We are just beginning to explore the extraordinary diversity and potential of marine phytoplanktonic eukaryotes.