A tattoo artist injects ink into the dermis of the skin, so the ink is visible through the epidermis but deep enough in the skin that it will not slough off. Tattoo artists push the ink into the dermis using a precise, automatic needle.
Tattoo ink is injected through the outer epidermis of the skin and into the dermis by a mechanical needle that punctures the skin and dispenses the ink pigments. Both the puncture from the needle and the foreign ink pigment particles attract white blood cells, which are called to heal the wound and destroy the ink. Because the ink particles are too big to be carried off by the white blood cells, they sit in the dermis.
As long as the ink is dispensed into the dermis, the tattoo remains relatively clear and permanent. Because the epidermis is made of dead skin cells stacked on top of each other to protect the skin's deeper layers, tattoos that are too shallow to reach beyond the epidermis eventually slough off. Tattoos that are injected too deep, so they reach beyond the dermis, can blur if the ink migrates.
The only way to get rid of tattoos is through laser treatment in which a laser beam strikes the ink and breaks it into pieces small enough for the white blood cells to dispose of it.