Every day, the members of the Microenvironment and Immunity Unit directed by Gérard Eberl at the Institut Pasteur focus their efforts on understanding the microbial mechanisms involved in diabetes, obesity, chronic childhood diseases, liver disease and colon cancer. This tireless team of scientists are constantly pushing their boundaries to improve their knowledge of the microbiota and unravel the interactions between the brain and the immune system, with the aim of shedding new light on neurodegenerative diseases. We take a visit to Gérard Eberl's laboratory.