PRO Iron (II,III) Oxide (Fe3O4) Nanopowders (NPs) are attractive nanomaterials due to their valuable properties, such as soft ferromagnetism, half-metallicity, and biocompatibility. Fe3O4 NPs have been intensively investigated because of their superparamagnety, high coercivity and low Curie temperature. Therefore, Fe3O4 NPs have brought out some new kinds of biomedical applications such as dynamic sealing, biosensors, contrasting agent in magnetic resonance (MR) imaging, localizer in therapeutic hyperthermia and magnetic targeted-drug delivery system, etc.