I did research between M1 & M2 under a really big-shot PI (highly respected in biotech industry, won the engineering version of the Nobel Prize, has been honored by Obama/Queen Elizabeth/world leaders, his tech is widely used by surgeons/physicians who don't know he's the inventor...). However, no physician I've ever spoken to has ever heard of him, and he's an engineer (not a physician). You're traditionally supposed to get letters from clinicians who've observed you (I have them already), I'm just really wondering how much a LOR from him would help with getting into a good residency?