A variety of lasers have been used specifically to treat pigmented skin lesions. These lasers are used to remove exogenous tattoo pigment as well as to treat skin disorders caused by endogenous melanin. Melanin is located within the melanosome, which is an organelle 0.5-1.0 mm in size. In laser treatment of pigmented skin lesions, the melanosome is the primary target structure for laser action. Melanin absorbs light at wavelengths ranging from the ultraviolet to the near-infrared, so there is a wide selection of lasers that can be used to treat melanin. The choice of therapeutic wavelengths is, in part, based on avoiding absorption peaks in other pigment groups. Based on the theoretical thermal relaxation time of melanosomes, the optimal pulse width is no more than 70-250 ns. Q-switched lasers are therefore ideally suited for targeting melanosomes. When the energy threshold for melanophore fragmentation is reached, the pigment cells die. The use of short pulsed lasers for tattoo treatment causes the ink particles to break up, selectively causing the death of pigment-containing cells and the release of pigment. There are several hypothesized mechanisms for the removal of pigment particles. Some ink (pigment) particles are removed by epidermal crusting, some by lymphatic drainage, and some by rephagocytosis by dermal cells. This is the reason why some patients do not have visible scab formation after the laser procedure, but still the pigmentation problem fades effectively. Different types of lasers are used to treat different pigmentation problems. the Q-switched ruby laser can reach energies of up to nearly 10J/cm2, emitting a deep red light of 694nm that is well-absorbed by melanin. With a pulse width of 20-40ns, this laser is effective in treating most tattoo colors except bright shades of red, yellow, etc. The Q-switched ruby laser is particularly effective in treating dermal melanosis such as nevus of Ota. The literature also includes many reports of successful treatment of sunspots and freckle-like nevi using the ruby laser. Milk café au lait spots and nevi have also responded to Q-switched ruby laser treatment (alternatively, the long-pulse-width ruby laser can be used to target nests of melanocytes to treat the nevus), but recurrences are common (dermal melanocytes are left behind when the laser is used to treat the nevus). The treatment of acquired pigmented nevi is controversial, and no histologic evaluation is available, but clinical outcomes are quite good. Of note, post-inflammatory hyperpigmentation and melasma respond poorly to ruby or other lasers.The Q-switched violet emerald green gemstone laser emits a deep red light at 755 nm with a pulse width of 50-100 ns, and its range of applicability is almost identical to that of the Q-switched ruby laser. Q-switched Nd:YAG lasers emit energy in the near-infrared wavelength range of 1064 nm, with a common pulse width of 10 ns. They are mainly used for treating dermal melanocytic nevus, such as nevus of Ota, and for removing blue-black tattoo pigment. 1064 nm light energy can be passed through a KTP crystal and then frequency-multiplied to produce 532 nm visible green light. This frequency-doubled Nd:YAG laser can effectively remove epidermal melanin, as well as red and yellow tattoo inks, but is not effective on green tattoos. Complications that may occur when treating with higher energies are hypopigmentation or hyperpigmentation, and temporary skin texture changes.