Even in the 1940s, humans discovered lasers! This magical light is the magnified light radiated by matter, called laser. Light is composed of photons, and each photon contains a certain amount of energy, so the photons are also called photons. Lasers are also made up of photons. In medicine, lasers are used to irradiate the blood, and the light is absorbed by the blood molecules and converted into molecular internal energy, thus playing the role of starting blood cells. Photons can also produce other photochemical reactions and biological effects on blood. The therapy that uses these effects to treat disease and health is called photon hemotherapy (also known as laser therapy).