Modern tattoo machine in use: here outfitted with a 5-needle setup, but number of needles depends on size and shading desired
Some tribal cultures traditionally created tattoos by cutting designs into the skin and rubbing the resulting wound with ink, as

A tattoo on the right arm of a Scythian chieftain, whose mummy was discovered at Pazyryk, Russia
Tattooing has been a Eurasian practice at least since Neolithic times.

A tattoo is a permanent marking made by inserting ink into the layers of skin to change the pigment for decorative or other reasons.