Magnetic Particle Imaging (MPI) is a novel imaging modality that uses various static and oscillating magnetic fields to image the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIOs) with high sensitivity, no tissue background, and no ionizing radiation. The method exploits the non-linear magnetization behavior of the SPIOs, and has shown great potential to surpass current in vivo imaging modalities in terms of sensitivity, safety, quantitation, and spatio-temporal resolution. MPI is well suited for clinical applications such as angiography, cancer imaging, and inflammation imaging; as well as research applications such as stem cell imaging and small animal imaging.