Invited Review by undergraduate student Brennan Ashwood and graduate student Marvin Pollum in the Crespo Group title “Photochemical and Photodynamical Properties of Sulfur-Substituted Nucleic Acid Bases”, among the top most cited articles in recent publication history of the Photochemistry & Photobiology journal of the American Society for Photobiology. This article was published as part of a Special Issue Celebrating Photochemistry & Photobiology’s 55th Anniversary.