Magnetic resonance imaging, or MRI, is a widely used medical tool for taking pictures of the insides of our body. One way to make MRI scans easier to read is through the use of contrast agents—magnetic dyes injected into the blood or given orally to patients that then travel to organs and tissues, making them easier to see. Recently, researchers have begun to develop next-generation contrast agents, such as magnetic nanoparticles, that can be directed specifically to sites of interest, such as tumors.