Over the past two decades, iron oxide nanoparticles for biomedical use had increased dramatically, largely due to its ability of non-invasive imaging, targeting and triggering drug release, or cancer therapy. Stem or immune cell could be marked with iron oxide nanoparticles to be detected by Magnetic resonance imaging (MDR). However, the concentration of iron oxide nanoparticles needs to be high enough to enable the significant detection by MDR. Due to the limited understanding of physicochemical nature of iro oxide nanoparticles in biological systems, more research is needed to ensure nanoparticles can be controlled under certain conditions for medical usage without posing harm to human.