It’s not just because of the caffeine though, it turns out that even spilled coffee fuels research.Most people are annoyed by nagging coffee stains, but to physicist Sidney Nagel they were inspiration. If you’re a coffee lover (or you live with one), I guarantee that you’ve seen the characteristic light brown stain with dark edges. I assume it was after he’d already had his morning coffee that this color difference piqued Nagel’s interest. Its brownish color comes from the tiny particles of coffee beans that make it through your filter and spread out in the water. During a meeting with her advisor one day, Shi accidentally spilled some coffee.