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Artists create tattoos by injecting ink into a person's skin. To do this, they use an electrically powered tattoo machine that resembles (and sounds like) a dental drill. The machine moves a solid needle up and down to puncture the skin between 50 and 3,000 times per minute.

The needle penetrates the skin by about a millimetre and deposits a drop of insoluble ink into the skin with each puncture. The tattoo machine has remained relatively unchanged since its invention by Samuel O'Reilly in the late 1800s.

O'Reilly based his design on the autographic printer, an engraving machine invented by Thomas Edison. Edison created the printer to engrave hard surfaces. O'Reilly modified Edison's machine by changing the tube system and modifying its rotary-driven electromagnetic oscillating unit to enable the machine to drive the needle. A tattoo machine creates a puncture wound every time it injects a drop of ink into the skin.

Since any puncture wound has the potential for infection and disease transmission, much of the application process focuses on safety. Tattoo artists use sterilization, disposable materials and hand sanitation to protect themselves and their clients.