Yasmine Belkaid's landmark advances have markedly altered our understanding of factors controlling host-microbe interactions. She pioneered the exploration of specific host-microbe interactions in different tissues. She identified immune mediators of pathogen persistence and factors controlling the induction of regulatory T cells. Turning to the interplay between nutrition and the immune system, she identified a role for defined metabolites in the control of both tolerance and immunity. Finally, she showed that the microbiota is required both for immunity to pathogens and for tissue repair.