Tattoo removal is the process of removing an unwanted tattoo. The process of tattooing generally creates permanent markings in the skin, but people have attempted many methods to try to hide or destroy tattoos. The standard modern method is the non-invasive removal of tattoo pigment using Q-switched lasers. Different types of Q-switched lasers are used to target different colors of tattoo ink; depending on the specific light absorption spectra of the tattoo pigments. Typically, black and other darker-colored inks can be removed completely using Q-switched lasers, while lighter colors, such as yellows and greens, are very difficult to remove. Success can depend on a wide variety of factors including skin color, ink color, and the depth at which the ink was applied. Recent research has investigated the potential of multi-pass treatments and the use of picosecond laser technology. Historical methods Before tattoo removal with Q-switched lasers began in the early 1990s, continuous-wave lasers were the standard method for tattoo removal. Continuous-wave lasers used a high energy beam that ablated the target area and destroyed surrounding tissue structures as well as tattoo ink. Treatment tended to be painful and cause significant scarring. Prior to the development of laser tattoo removal methods, common techniques included dermabrasion, TCA (Trichloroacetic acid, an acid that removes the top layers of skin, reaching as deep as the layer in which the tattoo ink resides), Sal abrasion (scrubbing the skin with salt), cryosurgery, and excision, which is sometimes still used along with skin grafts for larger tattoos. Many other methods for removing tattoos have been suggested historically, including the injection or application of tannic acid, lemon juice, garlic, and pigeon dung. Motives A poll conducted in January 2012 by Harris Interactive reported that 1 in 7 (14%) of the 21% of American adults who have a tattoo regret getting one. The poll did not report the reasons for these regrets, but a poll that was conducted four years prior reported that the most common reasons were "too young when I got the tattoo" (20%), "it's permanent," "I'm marked for life" (19%), and "I just don't like it" (18%). An earlier poll showed that 19% of Britons with tattoos experienced regret, as did 11% of Italians with tattoos. Surveys of tattoo removal patients conducted in 1996 and 2006 provided more insight. Of those polled, the patients who regretted their tattoos typically obtained their tattoos in their late teens