Nanomaterials have been considered for a long time to be interesting for medical imaging due to their unique properties, they range from 1-100 nanometers in size, a billion times smaller than a meter. Nanoparticles can be designed in such a way that gives them the ability to perform multiple types of imaging, this is where our research comes into play. In this research proposal we aim to create a product which can (1) target cancer cells, (2) provide contrast for x-ray CT (computed tomography) scans and is fluorescent (visible light). For this task, we have chosen hafnium oxide nanoparticles because they are stable, biocompatible, and very small. Hafnium has a high density, it provides (as shown by our preliminary data) better CT contrast than products currently used in the clinic. To provide the fluorescence functionality, we insert lanthanide atoms within the particle, a process which is referred to as "doping". To protect these atoms from the surrounding environment we will "shell" the particles with another layer of hafnium oxide, you can compare it to protecting food by packaging it. Next, we attach molecules to the surface of the particles that allow the nanoparticles (which are a solid) to behave as large molecules in water. These molecules can be further adjusted to allow the particles to target cancer cells. Finally, we will test their performance on healthy cells, cancer cells, healthy mice and mice with tumors.