Superparamagnetic iron oxide nanoparticles (SPIONs) resemble a unique class of nanomaterials with distinguished magnetic properties and biocompatibility, thus they have recently grasped the attention of researchers. SPIONs have various applications in fields such as -but not limited to - diagnostics, drug delivery, biosensing and bioimaging. The ability to control these nanoparticles by applying an external magnetic field made them perfect nanomaterials for such wide range of applications. Moreover, SPIONs have unique surface chemistry allowing for surface functionalization/coating with different organic or inorganic materials and thus making them suitable for different aspects. This review summarizes the most recent methods proposed for synthesizing SPIONs suitable for different applications. In addition, the amazing properties of SPIONs are discussed herein. Finally, an overview about some of the recent applications of SPIONs is introduced.