Different people may have different ideas when it comes to lasers. In fact, since Einstein proposed the laser theory in the 19th century, scientists have been constantly researching this newborn thing, and now the application of lasers has penetrated into all areas of society, from the most mysterious military to the most common children’s laser toy lights. The following is an introduction to the dermatology laser inside medicine. Laser, also known as radium in Hong Kong and Taiwan, is a different from sunlight and light, with a high degree of parallelism, high coherence, high brightness, a single color of a single wavelength of light, simply put sunlight drinking light is a collection of many kinds of light, laser is one of those many kinds of light. Because of the single wavelength, it is highly targeted. Among the lasers in dermatology, there are Q-switched lasers for pigmentation caused by skin melanin aggregation such as freckles, melasma, coffee spots, nevus of Ota, nevus of Ito, pigmented gross epidermal nevus and tattoos; there are dye lasers for vascular abnormalities caused by angiomas, nevus of vivid redness, capillary dilation, spider nevus, etc.; there are bait lasers and CO2 lasers for scarring, skin laxity and skin redundancy; there are semiconductor lasers for hair removal There are also the semiconductor lasers for hair removal, and the Intense Pulsed Light which is now popular for comprehensive improvement of skin discoloration, wrinkles and enlarged pores, etc. In the decades of dermatology laser development, the pioneers of unremitting efforts, continuous improvement, now the dermatology laser has been able to remove lesions without leaving traces, no longer like in the past to remove a spot to leave a scar, to remove a tattoo to leave a scar, to remove a mole to leave a scar!