Darwin's 1837 sketch of a phylogenetic tree. (By Walt at Nola Tattoo.
It is the algebraic equation that finishes a heart on a graph. I like this idea because I'm a math geek but I would get an algebraic equation that's answer would be "infinite solutions"
Plus her new tattoo of her grandma on her arm and the cat on her lip and the one of Floyd and the cresent moon and the 'love yer brain'.