Extensive studies were devoted to iron oxide nanoparticles (IONPs), in recent years. Iron oxides are chemical compounds that have various polymorphic forms, including maghemite (γ-Fe2O3), magnetite (Fe3O4), and Hematite (α-Fe2O3). Among them, the most important studied is magnetite (Fe3O4) due to its low cost and low toxicity, besides its unique magnetic and physicochemical characteristics which qualified it for use in various applications such as biomedical and technological applications. Magnetic particles should be small and have a narrow size distribution for these applications. The smaller the size of the iron oxide particles, the greater their reactivity and biodegradability. In this review, we display summary information of magnetite (Fe3O4) nanoparticles in terms of structure, characteristics, and preparation methods.   Because the prepared strategy has been proven to be critical for preferable control of the particle size and shape, in addition, to producing monodispersed magnetite (Fe3O4) nanoparticles with a direct effect on their characteristics and applications, special attention will be placed on chemical preparation techniques including Hydrothermal synthesis, Co-precipitation technique, Sol-Gel process, and thermal decomposition method. This review offers specific information for selecting appropriate synthetic methods for obtaining appropriate sizes, shapes, and magnetic properties of magnetite (Fe3O4) nanoparticles (NPs) for target applications.