In this episode, we talk about ways in which light-matter interactions are revolutionizing surgery.  We are joined by Christie Lin,  VP of Research at OnLume - a startup based in Madison WI dedicated to improving patient outcomes through innovations in Fluorescence Guided Surgery (FGS).  Christie prompts us to revisit some of our favorite topics, including SWIR fluorophores and gamma rays, and she also introduces us to regulatory policy for combination drug and medical devices!  The results of our first ever Twitter poll are announced,  and we finally answer a question that has been vexing us since Episode 1: How DO you focus a proton beam?  The answer might leave you speechless.