HDAC9 and neoplasm: Zhang et al. demonstrated photo-uncaging by longer wavelength green light irradiation by introducing a BODIPY group to the valproic acid (VPA) drug via a light-cleavable N–O linkage.100 VPA has shown potential as an anticancer agent due to its ability to inhibit histone deacetylase (HDAC) and induce apoptosis; however, its direct administration is associated with severe side effects.101 In their case, the caged VPA was efficiently taken up by tumor cells as observed from microscopy images and remained inactive in the dark.