Very Short Introductions: Brilliant, Sharp, Inspiring The term 'microbiomes' encapsulates an important scientific breakthrough of recent years. This is the realization that humans, other animals, and plants harbour communities of microorganisms which are mostly beneficial but can occasionally cause or exacerbate disease. Our quickly developing understanding of microbiomes is being translated into novel microbial therapies for human disease and is contributing to sustainable practices in agriculture and food production. On the flipside, there is a growing concern that some claims for microbiomes, especially in relation to human health, far exceed the scientific data. This Very Short Introduction is an essential guide to the fast-moving discipline of microbiome science. It accessibly distills the key facts about our resident microbiomes, explains how and why our health and wellbeing depend on them, and provides readers with the fundamental knowledge they need to judge the reliability of