Well-defined photochromic hybrid materials have been prepared by embedding spirooxazine dyes into matrices made of {(BuSn)(12)-O-14(OH)(6)}(2+) nano-building blocks assembled with alpha,omega-carboxymethyl poly(ethylene glycol) macromonomers (see Figure). Processed as 2-3 mum thick films, these materials exhibit fast and direct photochromism.