The focus of research in the Chisholm Laboratory is the marine microorganism, Prochlorococcus. This microbe is the dominant primary producer in the oceans, the smallest known phototroph, and the most abundant photosynthetic cell on the planet. Over the past fifteen years we have been developing Prochlorococcus as a model system for cross-scale systems biology by studying it from the genome to global scale. We are studying its genomic diversity, the functional and ecological implications therein, and the cell’s meta-metabolism in in the context of the community of microbes it is part of in the wild. We also study the role of phage in shaping genomes and populations. Thus we use Prochlorococcus to help us understand the forces that shape life, in all of its dimensions. While DNA contains the information that builds life’s machinery, it is higher order interactions in ecosystems that shape, through natural selection, the features of this information. This type of integrated understanding will facilitate advances across all realms of the life sciences – both basic and applied.