Water interacts with metal ions in a variety of contexts: from aqueous solutions of inorganic salts to enzymatic catalysis. The investigation of water-metal ion interactions is conveniently performed through water 1H NMR at different magnetic field—a technique known as relaxometry. Advances in Inorganic Chemistry, Volume 57 focuses on relaxometry of water-metal ion interactions.Contributions by leading experts in the field cover important advances in inorganic and bioinorganic chemistry; another welcomed addition to the widely acclaimed series, Advances in Inorganic Chemistry.