Ink containing not only colour pigments, but also fluorescent substances (pigments), used to print both text and motifs, is called fluorescent ink. This type of ink is visible under normal light and fluoresces under UV light. Fluorescence is a short-lived light emission which ceases to glow practically immediately after the illuminating light source has been extinguished. Bifluorescent inks emit fluorescent light of different colours when exposed to UV light in 365/254 nm wavelength.  These inks are easy to verify and difficult to reproduce. Tri-fluorescent inks display different luminescences under 365/313/254 nm illumination. The quadro fluorescent ink is an even more sophisticated one. It shows an additional anti-Stokes luminescence compared to our tri-fluorescent ink. These inks are to be activated with IR irradiation and are able to emit not only green but orange and blue light as well.