The principle of selective thermolysis can be applied towards the removal of tattoos. The energy delivered by a number of different lasers is targeted towards the carbon particles or dyes that are found in skin tattoos, allowing selective destruction of the foreign pigment while minimizing damage to the surrounding skin. 

The laser device fragments the ink with short pulses of intense, concentrated laser light. The method of delivery and the wavelengths used are designed to target only the tattooed pigments, without affecting the surrounding pigments and layers of skin. Different laser lights are used for different ink colors. Black ink is easiest to remove, because black absorbs the full spectrum of light, while green, blue, red, and other colors require more targeted laser pulses.

Passing through the surface layers of your skin, the light is absorbed by the tattooed pigments, causing them to break into smaller particles. Your body's immune system then removes the fragmented tattooed particles. And because your immune system works best in areas of greater blood circulation, ink can be removed faster in those areas. Thus, it's more difficult to remove tattoos in the hands and feet, where there is less circulation.

Tattoo removal may require anywhere from one to nine laser treatment sessions, each treatment lasting only a few minutes, with four- to eight-week intervals between each session. Each treatment penetrates a little deeper, removing more ink and leaving the tattoo progressively lighter.

After the procedure, you'll be given anti-bacterial ointment and bandaging on the treated area. Your doctor may instruct you to keep the treated area elevated to avoid swelling, and to avoid the sun, as your skin will be extra sensitive to sun damage. You may feel a slight sunburn sensation for a couple of days and have redness for a few weeks.

The use of laser in tattoo removal really constitutes a leap forward compared to other methods such as microdermabrasion or even earlier, skin excision and is regarded today as the easiest and most effective way to remove an unwanted tattoo.