light causes demolish theory: MV system and HONKON system laser treatment instrument adopt particular crystal Q mode,the pigmentation in the lesion tissues could be effectively broken up intopieces and removed by taking advantage of the high energy immediated by laser,which is the socalled the explosion principle.One part of the pigment will split into the tiny granules that can be engulfed by phagocytes of the body.After the digestion of phagocytes,it can be excluded from the lymphatic system of the body.The pigment of the injured tisssues gradually becomes shallow until disappears ,while no injured trace will be left on the peripheral normal tissues,for they wil not absorb the laser of the fixed wavelength.