Q-switched lasers are able to emit energy in millionths of a second. Given the extremely short duration of the impulse, if just 1 joule of energy were emitted, it would be as though the target had been impacted by enough energy to illuminate the city of Milan for 17 hours. The targets are pigment granules, both endogenous (melanin) and exogenous (tattoo pigment). The pigment is fragmented by photomechanical effect, and the tiny granules are eliminated, either directly expelled from the skin or eliminated by other cells called mastocytes, through a process called phagocytosis. The very brief duration of the impulse also means that damage can be confined to the targets, without heat dispersion affecting the surrounding tissues. Q-switched lasers are the only equipment that can be used to remove tattoos and are also extremely valid in removal of lentigo (liver spots) above all on the face and the back of the hands.