Previous works postulated that AuNPs catalyze Azo Z-E isomerization in the dark via electron transfer. As presented by Mulvaney and coworkers, electron transfer from AuNRs can be confirmed by redshift of the l-LSPR band. Indeed, we observed such spectral change (ca. 1.8 nm) upon Azo isomerization in the dark (Figure ). Hence, our results indicate the eT mechanism, although there are three general differences between our and former contributions. ). CNFs do not exhibit any electron-donating character, and hence, their catalytic influence on the AzoGly isomerization is ruled out. Since AzoGly is tethered to CNFs via a glycinelike side group, its movement and steric freedom are limited. At the same time, CNFs form an entangled network, contributing to the steric hindrance and confinement experienced by Azo molecules. Logically, the more CNFs we use, the denser the network created by the fibers. Thus, by changing CNFs content, we also supposedly change the environmental constraint imposed on AzoGly, which results in the differences in the kinetics of thermal back-isomerization. This is coherent with azobenzenes' tendency to exhibit decreased switchability without a high degree of conformational freedom. However, we assume that the nature of confinement imposed on AzoGly in this system is not too rigid, as the photoswitchability of the photochromic component remains distinct and stable (Figure ). Moreover, it is possible that interactions between hydroxyl groups of CNFs and N=N bond also contribute to the dramatic decrease of the τ1/2, similar to Azo isomerization in the presence of background ligands. Presented thermal relaxations of AzoGly-Au-2-CNFs constitute valid points for further development of hybrid materials with desired stabilities of photochromic components. We