This book discusses the inherent need for and significance of metal ions in metabolic reactions. It details their essential elements and mechanistic prospects in regulating biological reactions, as well as covers the broad domain of elements, including main group as well as transition elements, in a comparative and comprehensive manner. Contemporary and advanced topics, such as nuclear medicine and biomineralization, are also covered. Features: Highlights the different behaviors of Fe/Cu proteins and the structural changes during their biological functioning Discusses the mechanistic prospects of various enzymes and proteins, e.g., Cu-Zn SOD, zinc finger, and ionophores Explores the chemical and biological prospects of trace and ultra-trace elements Includes biomimetic models of iron and copper Reviews the criteria for nature selecting metal ions, why only certain elements are essential, and the differences between biologically induced and biologically controlled biomineralization This book is aimed at graduate students and researchers in chemical engineering, materials science, chemistry, and biological sciences.