Tattoos: The science behind getting inked

Everyone knows that getting a tattoo is supposed to hurt, but not many know the science behind the process.

In order for a tattoo to be permanent, ink has to get into the dermis.

The dermis is the tissue underneath the outer layer of your skin, called the epidermis.

To transfer ink into the dermis, a tattoo artist makes thousands of tiny pricks in the skin.

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The artist does this by dipping a needle in ink and turning on a rotary motor which quickly jabs ink into the dermis over and over.

Modern tattoo machines pierce the skin at a frequency of 50 to three thousand times per minute.

A needle used for lining will have few ends, but a needle for coloring or shading can have anywhere up to 25 ends.

These ends create thousands of tiny wounds in the skin, which puts the body's immune system into hyperdrive.

Blood cells called macrophages go to the site of the wound and engulf the ink particles, fading the tattoo over time.

These engulfed ink particles go through the lymphatic system and are excreted by the liver.

But the macrophages that don't make it back remain in the dermis, leaving some of the ink and making your tattoo permanent.

Click through the gallery below to see photos of 3D tattoos: