A challenge with stem cell therapy is identifying where the injected cells will travel; one potential solution is the use of fluorescent biomarkers. In vivo they would give their target a fluorescent color which can be identified using a microscope equipped with a fluorescent filter, this would allow researchers to see if the cells have reached the targeted area, from there they will be able to modify the procedure, making it more effective. Fluorescein isothiocyanate or (FITC) has proven to be a potential biomarker because of its low toxicity [1]. When FITC is combined with mesoporous silica nanoparticles and capped with a contrast agent such as Bismuth, it produces a very effective tag. We have tested these fluorescent nanoparticles at various doses with mesenchymal stem cells, these stem cells can not only give rise to bone marrow, cartilage, and fat cells, but they also support hematopoietic stem cells [2].First the cells were trypsanized then seeded onto a 24 well plate; this allowed us to see if there was an uptake of the fluorescent nanoparticles by the cells and if they were still viable at the various doses. Images of the tagged stem cells were taken at 20x magnification with a microscope equipped with a fluorescent filter. The pictures were analyzed using both CellProfiler and ImageJ computer software.  The goal of this experiment is to see the highest dosage of fluorescent nanoparticles we can expose the stem cells to without killing them.