In this episode, Martin Kiernan talks to Dr Sarah Fieldhouse, Associate Professor of Forensic Science and Dr Emmanuel Babafemi, Senior Lecturer in Biomedical Sciences both of the University of Staffordshire, UK. We discuss a recent paper looking at hospital cleanliness. Using forensic light, the study uncovered invisible contamination on surfaces that looked clean to the naked eye. We discuss what fluorescence reveals, what ATP misses, and how this approach could reshape environmental monitoring in healthcare.The open access paper is available here:Fieldhouse S, Bastaki BB, Ledgerton A, Clarke P, Lewis T. Assessing the effectiveness of hospital cleaning using fluorescence: a proof-of-concept study and comparison with ATP testing. J Hosp Infect 2025;https://www.journalofhospitalinfection.com/action/showPdf?pii=S0195-6701%2825%2900267-1