Over 1.5 billion years ago the most important evolutionary transition in the history of life occurred, leading to complex/compartmentalized cellular forms -the eukaryotes. The aim of my research is to understand the evolution and diversification of this form. The vast majority of the diversity of life on Earth is microbial, yet only a small proportion of this diversity has been studied. This is because most microbial forms cannot be propagated into culture in the laboratory. To study this hidden majority we sample cells or DNA directly from the environment and use these data to investigate the diversity, evolution and functional capacity of previously unsampled microbial lineages allowing us to fill in many missing branches on the tree of life.