Superparamagnetic iron oxide nanoparticles (SPION) have been evaluated for a variety of biomedical applications, including magnetic particle imaging (MPI), magnetic resonance imaging (MRI), and magnetic fluid hyperthermia (MFH). Although many iron oxide nanoparticles have been designed, developed, and marketed, due to their widespread use especially in promising new modalities such as MPI, further research on the optimization of their synthesis and performance is inevitable. The overall goal of this book is to express the obtained results of the development of high-performance SPION for MPI, MRI, and MFH applications, and comparison of their properties to widely used commercial formulations, such as Resovist®, Sinerem®, and Perimag®.