Modern Tattooing
Thanks to Sean Beck
HowStuffWorks would like to thank Sean Beck of the Naked Art tattoo parlor (located in Raleigh, NC) for his help in creating this article.
Today, tattoos are created by injecting ink into the skin. Injection is done by a needle attached to a hand-held tool. The tool moves the needle up and down at a rate of several hundred vibrations per minute and penetrates the skin by about one millimeter.

What you see when you look at a tattoo is the ink that's left in the skin after the tattooing. The ink is not in the epidermis, which is the layer of skin that we see and the skin that gets replaced constantly, but instead intermingles with cells in the dermis and shows through the epidermis.

The tattoo needle inserts ink into the skin's dermal layer.

The cells of the dermis are remarkably stable, so the tattoo's ink will last, with minor fading and dispersion, for your entire life!