Enzymes are proteins that catalyze non-spontaneous organic reactions in physiological conditions. Remarkably the water-insoluble organic substrates are usually encapsulated in hydrophobic proteincavities, which constitute reaction hotspots in enzymes. We have devised a newcatalyticphotoredox paradigm using water-soluble cationic nanocages [1] that mimic the enzyme cavity whileproviding a modular host-guest photoactivation strategy. [2, 3, 4] Through the potent combinationof light activation and substrate pre-organization in water, we demonstrate facile yet selectiveaerobic oxidation of hydrocarbon C-H bonds and oxidative C-C coupling under ambient conditionsusing proton-coupled electron transfer (PCET) [ 2, 3, 5, 6, 7, 8] along with usage of cage for tamingaqueous reactivity high valent metal-superoxo complex.[9] Here we show host-guest CT states canbe used to drive non-redox reactions as well: cis-to-trans photoisomerization of stilbene derivativesinside water-soluble nanosized cages to 100% yields.[10] I will discuss the critical role of thecage- size and electronics that dictate product selectivity while avoiding photostationary states in aqueoussolutions thereby mimicking the natural opsins.