Magnetic nanoparticles (MNPs) are one of the materials of great interest for presenting a unique combination of relevant properties such as high surface area, magnetic behaviour and low toxicity, which can find potential use in different processes and applications in areas such as catalysis, data storage, water treatment, drug delivery system, DNA separation, tissue engineering, sensors, hyperthermia, ferrofluids, and as contrast agents in nuclear magnetic resonance (NMR) imaging. This book provides further information on how magnetic nanoparticles are synthesised, their physicochemical properties and the roles MNPs play in biomedicine.