LASER stands for Light Amplification by the Stimulated Emission of Radiation. Laser produces a single wave-length (colour) of light that can be sharply focused and very powerful, powerful enough to cut steel. Different substances absorb laser light preferentially. When the energy of a laser beam is absorbed, the material will generally heat up. By controlling the power of the laser, the length of the pulse, the size of the laser beam and other factors, different effects can be made to the substance (or tissue).