It's time to think about circadian rhythms.

We here introduce a Review Series focussing on the important influences circadian rhythms have on immune responses. The three reviews in this series, expertly curated by Rachel Edgar, discuss how the cyclic oscillations in our cellular clock affect the innate and adaptive immune response, and how interactions with the intestinal microbiota, themselves subject to daily oscillations, also influence immune responses. As we understand more about these mechanisms, by which chronobiology contributes to immunology, it is becoming increasingly clear that they have important functions in maintaining health, influence autoimmunity and may contribute to the effectiveness of vaccinations.