Researchers describe how gut-on-a-chip devices can bridge lab models and human biology. Modeling the microbiome is particularly difficult because of its unique environmental conditions, but through creative design, gut-on-a-chip devices can simulate many of these properties, such as the gut’s anaerobic atmosphere, fluid flow, and pulses of contraction/relaxation. Growing intestinal cells in this environment means that they more closely resemble human biology compared to standard laboratory cell cultures.