Neon tubes are gas discharge tubes filled with neon. They are often used as illuminant for luminous advertising. Excited atoms release a characteristic wavelength during their return to the basic state of electromagnetic radiation. In the plasma, this procedure proceeds continuously. Noble gases such as neon are monoatomic gases, which is why they radiate only with a characteristic wavelength and therefore with clear and bright colours. For this reason, gas discharge tubes filled with noble gas are often used as fluorescent tubes.