Luminol is a chemical reagent that is used to locate possible areas of latent or invisible blood. This is one of the most commonly depicted forensic techniques on TV shows! The reaction produces a characteristic luminescent glow. Even after all visible signs of blood were wiped away on the third tile, we can still see the luminescent reaction. At a crime scene, this would indicate to us that that is an area we should focus on for further sample collection and testing! #YouThoughtYouCleanedItGood