Photochromic nanoparticle inks could make tattoos rewritable

Programmable pigments: Photochromic nanoparticle inks for rewritable tattoos

Researchers propose photochromic nanoparticle inks that let tattoos be rewritten on demand, according to a Hacker News discussion of a Cell paper. The concept points to programmable pigments whose appearance can be switched after application, potentially turning body art into a reversible, updatable medium.