Marine microeukaryotes navigate constant fluctuations in food, friends, and foes to produce and to distribute crucial resources that support oceanic life and impact global climate. The molecular mechanisms that enable microeukaryotes to perform multifaceted functions in dynamic environments remain unexplored, primarily due to a historic inability to recapitulate environmental behaviors and to perform genetics. My lab innovates genetic tools for a key group of marine microeukaryotes, the choanoflagellates, to discover genetic pathways for the differentiation of distinct cell types that exploit environmental niches. By directly connecting genes to their environmental functions, we aim to illuminate how past and present genetic innovations and climactic transformations have facilitated major evolutionary transitions–particularly the origin of choanoflagellates and their closest living relatives, animals–and may shape modern marine ecosystems under mounting anthropogenic pressures.