Don: Shh! I'm watching my favorite TV police drama: Crime Lab!

Y: Oh, cool. Hey, what's that guy doing?

D: Y'know Ya?l, you do have the right to remain silent...

Y: Why is he spraying that stuff on the ground?

D: You're not gonna clam up until I explain this, are you?

Y: Probably not.

D: All right, fine. I just happen to be a regular reader of the "Crime Lab" website, so I know all about police forensics.

Y: Let's hear it, Sherlock.

D: The stuff being sprayed is called luminol. It's a chemical mixture used to detect traces of blood. See those glowing green splotches on the ground? That's where the perp-Y: "Perp"?

D: Yeah--perpetrator--that's what detectives call criminals. Anyway, that's where the perp tried to clean up his victim's blood, but some invisible traces of it remain behind. Spraying luminol on the traces makes them visible.

Y: Luminol, as in illuminate. I get it. So how does luminol work?

D: A chemical reaction occurs when luminol comes into contact with hemoglobin, an oxygen-carrying protein in blood. The iron in hemoglobin causes the chemicals in luminol to react, meaning that their atoms rearrange to form new molecules. Since the original chemical molecules had more energy than the newly created molecules, during the reaction the extra energy is disposed of in the form of light. It's the same thing that happens when fireflies glow.

Y: That's neat. Y'know, you would have made a good detective, Don.

D: Really?

Y: Sure. Tune in next week when Detective Glass solves yet another Moment of Science mystery!

D: I like the sound of that.