Carbon dots are an emerging and fascinating carbon-based material, characterized by nearly spherical shapes with size lower than 10 nm, characterized by excellent optical properties and intense fluorescence. Carbon dots are suitable for various applications, like in optoelectronics, photocatalysis, sensing, and, particularly in the biomedical field. Thanks to their biocompatibility and low toxicity, they can be employed as drug and gene carriers, perform antioxidant actions, and are useful in theranostic applications. Their fluorescence capability allows them to act as chemical probes for detecting specific metallic ions and for bioimaging. Another outstanding feature is the tunability of their properties. Tuning of the carbon dots properties can be achieved by tailoring their composition, chemical structure, and size within the range 10-80 nm.