CDs are carbonaceous materials with nanometrical dimensions commonly defined as zero-dimension materials. These materials are biocompatible, easy to prepare, photostable and their production cost is relatively low. However, photoluminescence is undeniably the most compelling feature of the material, rendering its application suitable for the bioimaging and the theragnostic field. The variables in the creation of a material with diagnostic and therapeutic purposes are countless. The perfect material has a good balance in its polarity to reach the cell in its environment, a high yield in its production, a high yield in the loading process, and it has to penetrate the cellular barrier easily among other things.