This short video shows the experimental TEA Laser in operation.  A TEA laser is a "Transverse Excitation in Atmosphere" device - a nitrogen laser which uses atmospheric nitrogen as the lasing medium.  Basically, one uses a high-voltage circuit with a low-induction capacitor to laser-stimulate air, since our air is roughly 78 percent nitrogen.  The beam is invisible, but if the beam strikes paper, on which yellow highlighter has been applied, then the beam produces a bright spot.  The beam wavelength is 337.1 nanometers, which is in the ultraviolet part of the spectrum of light.