From Rita Yates
Modern forms of tattoo removal use lasers that emit short pulses of intense light, which pass harmlessly through the top layers of the skin and are absorbed by the tattoo pigment. This causes the pigment to fragment into smaller particles, which are then absorbed into the bloodstream and removed by the body’s immune system. Different types of lasers work on different pigment colours and will cause the tattoo to fade gradually over multiple sessions.
Answered by Joanna Stass for Brain Dump in How It Works issue 104