This book is an ethnographic exploration of what it means to be human from a more-than-human perspective, the microbial perspective. It engages with the scientific study of the microbiome and the vast microbial biodiversity that surrounds and constitutes us. Microbes connect human bodies with the environment in which they live and have important implications for both human and environmental health. Scientists studying the microbiome are explorers of uncharted life and in this venture they are constrained by onto-epistemic working practices grounded in the reductionist paradigm of molecular biology. At the same time, however, they configure the microbiome ecosystem as an aspirational form of ecological co-habitation. The aim of the book is to critically explore the ethical, political and ontological implications of microbiome science in times of profound socio-technical and ecological transition and engage with them productively from an anthropological perspective. It suggests ways to revitalize current debates within medical anthropology, environmental anthropology, science and technology studies and anthropology at large, especially with regard to posthumanism, the ontological turn and critical data study.