Most superheroes aren't scientifically accurate. That said, that doesn't mean that we can't let a biologist try to speculate how they might work in the real world.
Watch as Stanford biologist Sebastian Alvarado tries to unravel the biological secrets behind two of Marvel's top heroes — Captain America and the Hulk. Again, this is just a thought experiment, but it's one that helps you understand concepts like Chromothripsis, Epigenetic Modification, and Biliverdin!
Unfortunately, science still can't explain the Hulk's pants.