Comic book writers almost always spin up some inventive pseudo-science to explain how normal men and women transform into superheroes, but what if a real biologist took a crack at it? Sebastian Alvarado, a postdoctoral research fellow at Stanford University, has done just that with a new series of videos. He plumbs the depths of biology in a search for some sort of reality-based explanations for Captain America's and the Incredible Hulk's spectacular transformations. You might be surprised by what he finds. Just don't ask him to explain how Bruce Banner keeps his pants on.