The historical essence of drug discovery has been the search for molecules that interact with some specific biological target. Our laboratory is using a different approach: we develop relatively inert compounds that become active when exposed to light. Combined with the proper light exposure protocol, these compounds — or photosensitizers (PSs) — become potent anticancer or antibiotic agents. We have two effective approaches: synthetic compounds to target cancer cells (photodynamic therapy, PDT) and natural products for antibiotic activity (photodynamic inactivation, PDI). This work is inherently multidisciplinary, and our group uses methods from synthetic chemistry, photophysics and photochemistry, microscopy, cell culture, and laser spectroscopy in order to conceive, develop, and optimize new PSs and protocols. One of our synthetic compounds (TLD-1433) is currently in a human trial to treat bladder cancer, and our next-generation osmium compounds are not far behind.