Tattooing (also referred to as permanent make-up, microblading, cosmetic tattooing, micropigmentation) is any practice whereby a permanent skin marking or design is intentional introduction of tattoo ink into human skin.

Tattoo ink is a mixture consisting of colourants and auxiliary ingredients administered by intentional intradermal injection whereby a permanent skin marking or design (a “tattoo” or “permanent make-up”) is made.

“Colorant” is the commonly used denomination for pigments, lakes and dyes that are coloured molecules. Pigments are in general very poorly soluble in water and application media, and unlike most dyes, they have low solubility in organic solvents. For this reason, they remain essentially in the solid state, including in live tissues. Dyes are organic molecules that are soluble in general.

Auxiliary ingredients are necessary to obtain ready-to-use tattooing products. They are of different kinds like solvents, stabilisers, “wetting agents”, pH-regulators, emollients, and thickeners.

“Sterile” in this context means the absence of viable organisms, including viruses.