Surprisingly, it has everything to do with your immune system. Most people think a tattoo is permanent because the ink goes so deep into the skin that it cannot be washed off. It turns out there’s a lot more to it than that. Interestingly, your immune cells treat the ink like an infection, and they keep fighting it forever, which makes the tattoo last forever. Tattoo needles penetrate through the outer layer of your skin (called the epidermis), and deliver the ink into the deeper layer of skin (called the dermis), which contains nerves and blood vessels. As explained in the accompanying video, "Every time the needle penetrates, it causes a wound that alerts the body to begin the inflammatory process. That signal sends immune system cells racing to the site of the wound (or multiple wounds, in the case of the five-inch dragon breathing fire across your chest). Special cells called macrophages come to the rescue, eating up the dye in an attempt to "clean up" the inflammation it's causing. The rest of the dye gets soaked up by skin cells called fibroblasts. The fibroblasts, along with many of the macrophages, stay suspended in the dermis in perpetuity.” Isn’t that interesting? Watch this video [embed]https://www.youtube.com/watch?v=DMuBif1mJz0[/embed]