Highlighting significant advancements in the roles of certain metal ions in the conformational changes and function of cellular proteins, this volume discusses the mechanisms involved in the transport of metal ions into and out of target cells, particularly epithelial cells. It explains the role of key biologically relevant divalent metal ions involved in the molecular and cellular biology of various target cell populations. Although it primarily focuses on homeostatic metals such as nickel, zinc, and chromium, the text also discusses a few environmentally relevant toxic divalent cations, including mercury, cadmium, and arsenic.