developed photocage 36 (Figure 18), possessing the antitumor drug chlorambucil (cbl) linked to a rhodamine fluorophore via an ester bond, for the photo‐controlled release of cbl.[42] Photocage 36 in mitochondria of cancer cells is activated by oxidation with ROS to generate bright red fluorescing 36A. The gene discussed is CBL; the disease is cancer.