And while every teenage girl in the world probably knows all the boys' names, birthdays and favorite things (and anything slightly relevant in their lives), do you know which 1D member has "Might as well..." tatted on his hip?
Or which guy has a compass on his forearm? Or which one of the lads is sporting four bolded arrows?
Check out our gallery below and see if you know who is inked with what!
Gallery | Whose Ink is This? (One Direction Edition!)