ICG Azide is a copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) reagent of near infrared (NIR) fluorescent dye and used to generate a stable fluorescence signal in bioimaging. NIR fluorescence allows to observe the deep image from the surface of skin and being utilized in a wide range of research fields. The maxima of Ex/Em values are at 785/812 nm. ICG might be excited using 750-800 nm laser line or LED and displays excellent optical property. ICG azide couples with an alkyne to form 1,4-disubstituted 1,2,3-triazole inside of living systems without interfering native biochemical processes. Prior to perform CuAAC, counterpart alkyne functionality should be introduced onto biomolecule by means of chemical or genetic modification. We offer ICG azide as a click chemistry reagent dye for cellular imaging and nucleotide functionalization.