system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - If the human body replenishes its cells and has a new "set" every seven years, how do tattoos stay intact?

Sorry if this is a stupid question, I feel a bit dopey for asking! I read that the human body replenishes all of its cells as it grows (the Trigger's Broom thing) and that, on average, humans have a new set of skin cells every seven years. If this is true, how is it the case that tattoos stay intact when the skin cell is replaced? Obviously the ink isn't built into the cell itself, so how do they stay on the skin when the cells are brand new?

Apologies if I'm off-base on anything I've written :)
gpt
The ink from the tattoo is not part of your skin cells, the ink is lodged in between your skin cells. So you can replace all the skin cells you want and the ink will still be there.

Tattoos fade over time not because of skin cell regeneration, but because the body knows the ink molecules are foreign objects and your white blood cells will be chipping away at it for the rest of your life.