Presumably between their courses in snowboarding and advanced hydroponics, researchers at the University Of Colorado Boulder have developed tattoo ink that remains invisible until activated with UV light, and can be deactivated again with bright white (visible) light. Currently being tested before commercial availability, PhotoTats use inks with “photochromic (light reactive) dye in tiny plexiglass spheres.” No clue exactly how that works, but now I can finally get that MOM heart tattoo I’ve always wanted but hide it when I’m home visiting!

Video below, which includes handwriting on a hidden blotch of ink with a UV pen, and using stencils to make different tattoos from the same hidden ink.