Microorganisms live in biofilms—the equivalent of microbial "cities"—everywhere on Earth. These city-like structures protect and house microbial communities and play essential roles in enabling human and plant health on our planet. Now, a new Perspective article published in npj Biofilms and Microbiomes sets out a path to uncover the role of biofilms in health during long-duration spaceflight, and how spaceflight research can reshape our understanding of these microbial communities on Earth.