Fluorescence is a luminescence phenomenon in which a compound emits light after absorption of electromagnetic irradiation. Specialized terms such as photoluminescence, cathodoluminescence, anodoluminescence, radioluminescence, and x-ray fluorescence sometimes are used to indicate the type of exciting radiation. Fluorescence spectroscopy provides reliable quantitative and qualitative data. It precisely tracks chemical reactions from fluorescent materials compounds with aromatic groups, or conjugated planar, or cyclic molecules. It is up to 1000 times more sensitive than UV-vis or infrared spectroscopy. Fluorescence intensity depends on the fluorophore (compound that fluoresces), its concentration, excitation and emission wavelengths, temperature and contamination. We adjust the slit dimensions, photomultiplier tube voltage and bandpass filter cutoff to maximize the signal while avoiding saturating the detector. Together with x-ray diffraction, it is the most common spectroscopic technique with applications in geology, chemistry, medicine, and astronomy. A bibliometric analysis of the top 10 000 cited papers identified 5 clusters based on keywords centered around: (1) cancer, cells, and proteins; (2) aggregation induced emission, LED, and complexes; (3) live cells, sensors, and probes; (4) quantum dots, DNA, and biosensors; and (5) nanoparticles, in vivo, and drug delivery. Chemical engineers have yet to fully embrace fluorescence spectroscopy as the category is ranked 16th among all scientific categories that exploit it.