Each of the four general classes of laser (gas, solid, liquid, and semiconductor) emits a particular wavelength of light. This beam of light can be focused to a minutely accurate diameter and the depth of penetration can be controlled by the power input. Thus, there is minimal damage to surrounding tissue. A carbon dioxide laser was used to treat congenital hemangioma, verruca vulgaris, and condyloma acuminatum, and to remove tattoos. Of the four types of lesions treated, verruca vulgaris, condyloma acuminatum, and tattoos responded best.