Chinese Academy of Sciences Jul 3 2025 The human gut is home to trillions of microbes, yet scientific understanding has largely focused on bacteria, leaving the virome—the community of viruses—relatively uncharted. Bacteriophages, which infect bacteria, are the dominant members, outnumbering their bacterial hosts and subtly guiding microbial composition through predation and gene exchange. Eukaryotic viruses, meanwhile, influence immune responses and may trigger inflammation when balance is