The articles in this special issue attest to the fact that we are in the early stages of a scientific revolution in marine microbiology that is being fueled by vast quantities of new information derived from advances in microbiological techniques and genomic studies. Many new species, metabolic processes, and pathways in marine systems have recently been discovered. Subtle metabolic variations within and among species have also been revealed, and previously known genes and metabolisms have been detected in new environments. And this is just the tip of the iceberg. Using genome shotgun sequencing techniques, Venter et al. (2004) report finding 148 previously unknown bacterial phylotypes and over 1.2 million previously unknown genes, including more than 782 new rhodopsinlike photoreceptors (Figure 1)—just from surface-water samples from the Sargasso Sea (see also more recent articles by Rusch et al., 2007, and Yooseph, et al., 2007). The overwhelming challenge we face is how to make sense of all of this emerging information. What role do all these new genes and proteins play in driving marine-ecosystem dynamics and biogeochemical cycles? Which are important and which are not? What role are they likely to play in the evolution of marine microbial communities, how might they have influenced global biogeochemical cycles over Earth’s history, and how might they do so in the future?