Magnetic resonance imaging (MRI) is a medical imaging tool that can incorporate contrast agents to enhance its ability to identify and characterise pathologies. MRI contrast agents can be paramagnetic such as gadolinium, or superparamagnetic such as iron oxide. Significant concerns of Nephrogenic Systemic Fibrosis (NSF) have arisen involving gadolinium-based contrast media. Recent research has focused on iron oxide nanoparticles because their sizes are more comparable to biological units. These can give MRI the potential to detect a broader range of pathology, while also track and observe biological processes. This is the second article of a two-part series and will review iron oxide nanoparticles as a MRI contrast agent, and the potential applications of iron oxide nanoparticles to a range of pathologies and processes involving MRI.