Utilizing the explosive effect of the Nd: YAG laser, the laser lights permeate through the epidermis into the dermis and take effects on pigment mass. The laser energy is absorbed by the pigment. Since the laser pulse width is extremely short in nanoseconds and comes with super high energy, the pigment mass will swell quickly to break to small pieces, which will be eliminated by the body circulation system. Then the pigments become lighter gradually and finally disappear.