information:highlighting, information:extraction, information:filtering, structural:expansion, structural:scholar_edition
Process

Tattooing involves the placement of pigment into the skin's dermis, the layer of dermal tissue underlying the epidermis. After initial injection, pigment is dispersed throughout a homogenized damaged layer down through the epidermis and upper dermis, in both of which the presence of foreign material activates the immune system 's phagocytes to engulf the pigment particles. As healing proceeds, the damaged epidermis flakes away (eliminating surface pigment) while deeper in the skin granulation tissue forms, which is later converted to connective tissue by collagen growth. This mends the upper dermis, where pigment remains trapped within successive generations of macrophages, ultimately concentrating in a layer just below the dermis/epidermis boundary. Its presence there is stable, but in the long term (decades) the pigment tends to migrate deeper into the dermis, accounting for the degraded detail of old tattoos.

An alternative and painless method of permanent tattooing is to use patches covered by microneedles made of tattoo ink. The patch is pressed onto the skin the same way a temporary tattoo paper is applied to the body. The microneedles then dissolve, and after a few minutes the ink sinks into the skin.