The first laser for hair removal was approved in 1996, and since that time, light energy has been proven superior to any other hair removal therapy for treating large surface areas. Effective hair removal by light energy requires three elements: a chromophore in the follicle (in this case, melanin), a light source or laser with a wavelength that selectively targets the chromophore, and the appropriate parameters to heat sufficiently the follicle, without damaging the surrounding structures. A laser generates a monochromatic beam of light (a specific wavelength of light energy). Broadband light devices, also known as intense pulsed lights (IPLs), use filters to narrow down the light energy they deliver to a limited range of the spectrum. As with other laser- or light-based therapies, laser hair removal is based on the principle of selective photothermolysis, in which selective thermal damage of a pigmented target occurs when the target absorbs a wavelength of light energy delivered during a time less than or equal to the thermal relaxation time of the target. Long-term or permanent hair removal occurs with damage or destruction of the follicular stem cells, which are thought to reside in both the hair bulb and the outer root sheath of the bulge area, near the attachment of the arrector pili muscle. Light is absorbed by the melanin in the hair shaft and converted to heat, and the heat spreads out to the stem cells in the outer root sheath and damages the follicle.