text: Fluorescent properties in nanodiamonds arise from the presence of nitrogen-vacancy (NV) centers, nitrogen atoms next to a vacancy.  Fluorescent nanodiamond (FND) was invented in 2005 and has since been used in various fields of study. The invention received a US patent in 2008 , and a subsequent patent in 2012 . NV centers can be created by irradiating nanodiamonds with high-energy particles (electrons, protons, helium ions), followed by vacuum-annealing at 600–800°C. Irradiation forms vaccines in the diamond structure while vacuum-annealing migrates these vacancies, which will get trapped by nitrogen atoms within the nanodiamond. This process produces two types of NV centers. Two types of NV centers are formed—neutral (NV0) and negatively charged (NV–)—and these have different emission spectra. The NV– the center is of particular interest because it has an S = 1 spin ground state that can be spin-polarized by optical pumping and manipulated using electron paramagnetic resonance. Fluorescent nanodiamonds combine the advantages of semiconductor quantum dots (small size, high photostability, bright multicolor fluorescence) with biocompatibility, non-toxicity, and rich surface chemistry, which means that they have the potential to revolutionize Vivo imaging applications.