The DeLong lab's scientific interests focus primarily on questions in microbial biology. A large part of the lab's efforts have been devoted to the study of microbes and microbial processes in the ocean, combining both laboratory and field-based approaches. In addition to specifically examining the role of archaea in marine microbial communities, the DeLong Lab has focused on the development and application of genomic technologies to answer fundamental questions central to microbial ecology and evolution. Much of the biological complexity of microbial ecosystems is encoded within the collective genomes of the community. Just as individual macromolecules can serve as documents of evolutionary history, naturally occurring genomes can provide unprecedented perspective on environmental, evolutionary and ecological history. Recent applications in the marine environment demonstrate that our understanding of the functional attributes, population biology, and natural history of extant microbes can now be significantly advanced using these new approaches.