This reference provides the general reader with essentially an introduction to key ideas in quantum mechanics, and demonstrates the reality of such ideas in the existence of lasers. Although Albert Einstein published in 1917 a paper discussing stimulated and spontaneous emission of light, and although technology such as discharge tubes (eg, neon lights) were available at the time, it was not until 1960 that Theodore Maiman at Hughes Aircraft Corporation, demonstrated the first laser, albeit a ruby rod laser. If an electron in an atom is put into an excited state, then eventually that electron will drop to a more stable, lower energy state and emit a photon of light in the process. Einstein noted that a photon of the same energy as one that would be emitted could stimulate the atom to drop the electron to the lower energy state and emit the photon. If the technology is used to raise electrons into a higher state and then allow a chain reaction whereby released photons stimulate other atoms to release photons and so on, then laser light results. For example, we can pass an electric current through a neon tube to excite the electrons of the neon atoms into higher energy levels. Doing so results in a neon light-- electrons spontaneously drop to lower levels and photons are spontaneously emitted. However, if we then put mirrors at the end of the neon tube, then a photon reflecting off one of the mirrors back down the axis of the tube will stimulate another excited neon atom to emit a photon, and now there will be two photons travelling in the same direction, and will stimulate more neon atoms which will release more photons, and there will be more and more photons travelling together as the chain reaction proceeds. If one of the mirrors is partially reflecting and allows a small percent of the photons hitting it to pass out, then out of this mirror will emerge a laser beam.