Fluorescent nanoparticles are indispensable tools often utilised in analytical biology, fluorescence spectroscopy, bioimaging, biophysics, clinical diagnosis, and environmental sensing. Their specific photophysical properties, including brightness, emission wavelength, and analyte sensitivity, can be easily modulated. This affords fluorescent nanoparticles an expansive scope of applicability in imaging and sensing. This chapter gives an overview of various fluorescent carbon nanoparticles, supported by selected literature case examples, namely on carbon nano-onions, fluorescent carbon dots, and detonation nanodiamonds.