Diarylethene derivatives are a fascinating and high-performance family of photochromic molecules. When combined with fluorophores, they give rise to multiple intra- and intermolecular energy transfer processes, especially within molecular nanoparticles,[1] leading to giant amplification effects[2] or unprecedented zero-order photokinetics,[3] which are of particular interest in the super-resolution imaging area. Besides, when diarylethenes feature a protonatable group, their thermal back-reaction becomes controllable with catalytic amounts of acid, opening up extremely promising prospects in the field of molecular solar thermal (MOST) energy storage systems.[4] These different properties require an exploration of the elementary processes behind the effects observed at the macroscopic scale.[2-5]