Heavy metals essential to organisms are termed “biometals”. Bio-inorganic chemistry deals with the functions of biometals in vivo at an atomic to molecular level, while cellular regulation of biometals such as absorption and transport has been investigated in cell biology. Although these research fields have independently developed and matured, interdisciplinary information across these fields is required for a comprehensive understanding of the roles of biometals at atomic to molecular, cellular and organism levels.  Focusing on the biological significance of copper in our bodies, this book considers the maintenance of copper from different perspectives ranging from bio-inspired catalysts and mechanisms of copper proteins to pathological roles in diseases. Both quantity and quality of copper inside and outside the cell are essential for our health. Because of its high redox activity, copper acts as an active site for electron transfer and enzyme reactions in many proteins. Genetic and environmental disorders of copper metabolism are therefore associated with many diseases. In addition, copper-containing proteins are involved in the activation of molecular oxygen and have served as a good model for the development of inorganic copper complexes for industrial applications. Resulting from a 5-year project on Integrated Biometal Science in Japan, this book not only documents the latest research but also fills a gap between chemical understanding and our real life.