One Health (OH) is the conceptual and operational framework that links environment, food-producing organisms and human health. OH is a developing field, that deals with the multifaceted web of feed-backs and interactions among its components. In order to avoid “drowning into complexity”, priority issues should be identified, either for research and for risk analysis. To date OH approaches have frequently pivoted on infectious agents shared among animals and humans and the related problems, such as antibiotic resistance. Nevertheless, the OH scenarios include, and should increasingly include, environment-and-health problems. Food and environment do interact. Environment influences the living organisms that produce human food and, in the meanwhile, food production outputs influence the environmental quality; as for foods of animal origin, feed materials and practices are driving components of the environment-food interactions. In this book, we aimed at highlighting the importance of environment, chemical exposures and toxicological issues in the field of OH, as well as the need for multidisciplinary integration in order to support OH approaches into diseases prevention and health promotion.