In 1995, ruby laser (694nm) was used for unwanted hair removal In 1996, emerald (755nm), neodymium doped yttrium aluminum garnet laser (1064nm) were also used for unwanted hair removal; In 1998, semiconductor laser (810nm) was developed and applied for hair removal, and finally became the gold standard for wavelength of hair removal project. The first generation of laser hair removal devices 694nm, 755nm devices, designed with the concept of “burning” the hair follicles, using very high energy to heat the temperature of the hair follicles and hair root areas to 60-70 degrees Celsius, to achieve the effect of hair follicle destruction. The characteristics of this laser device are that the hair removal process is easy to cause burns and blisters, and the patient feels painful; the second generation of laser hair removal devices traditional semiconductor hair removal laser 810nm, although the risk of burns is reduced because of the poor absorption of melanin in the basal cell layer, but still slow and painful; the third generation of ice point hair removal laser design concept – low energy density, high average power, painless and fast hair removal. Painless and fast hair removal; Scientists have found that when the temperature of the hair follicle area is raised to about 45 degrees Celsius and maintained for a period of time, the hair follicle and the growth stem cells around the hair follicle will be destroyed and apoptosis will occur, achieving the purpose of removing unwanted hair.