Eukaryotes existed exclusively as microorganisms for a minimum of 500,000 to one billion years prior to the evolution of plants, animals and fungi. Understanding the evolutionary history of microbial eukaryotes, especially the protists, is key to understanding the origins of eukaryotes, the emergence of parasitism, and the evolution of this remarkably diverse assemblage into plants, animals, fungi and other recently derived groups. Protists represent an eclectic group of organisms marked by numerous innovations in body plans, ecology, biochemistry, and molecular processes. The transition from prokaryotic life-forms to eukaryotic cellular architecture, and the origins of multi-cellular eukaryotes are rooted in the world of protists. project describes the collection of new molecular data and the construction of a large-scale, multi-gene data set for exploring evolutionary relationships for diverse eukaryotes. Our experimental strategy seeks to capture the diversity of eukaryotes by exploring relationships within major clades, and by placing taxa of uncertain position on genealogies. We constructed cDNA libraries for over 20 key protists and sequenced 10,000-20,000 cDNA clones from each library. PI Mitchell L. Sogin Marine Biological Laboratory