“…Since the 1970s, a considerable effort has been dedicated both to the development of novel photoactivatable chemical probes and their applications in various experimental studies. Regarding the scope of PPG applications, the caged substrate could be as simple as a proton or an inorganic species or ion (e.g., Ca 2+ [15], Zn 2+ [16], CO [17], NO [18], H2S [19]), it could be a small molecule (e.g., second messenger (such as inositol-1,4,5-triphosphate (IP3) [20]), neurotransmitter (notably GABA and glutamate [21,22]), nucleotide [23], peptide [24], drug molecule [25] (such as antibiotics [26], analgesics [27] or anticancer agents [28]) or a more complex biomolecule (e.g., enzymes [29], RNA [30] or DNA [31]) (Figure 3). Examples of PPG applications for small molecules/inorganic species: (A) calcium caging with photoactivatable EGTA [32], (B) neurotransmitter glutamate caging with MNI [21], (C) caging the anticancer agent vemurafenib with a nitrobenzyl PPG [33], (D) a coumarin PPG-caged antibiotic agent [34], (E) a coumarin PPG-caged analgesic [27].…”