TheJournal of Fluorescences fourthWhos Who directory is to publish the names, contact details, specialty keywords, and a brief description of scientists employing fluorescence methodology and instrumentation in their working lives. In addition, the directory will provide company contact details with a brief list of fluorescence-related products. The directory will be edited by Chris D. Geddes and Joseph R. Lakowicz, editor and founding editor of theJournal of Fluorescence.