If you go to any outdoor, nighttime event these days, you’re likely to see people wearing glowing plastic necklaces. These necklaces seem to glow magically, as though they were made from cool, flexible neon lights. Each necklace is a hollow, plastic tube filled with chemicals–non-toxic, of course–and those chemicals are undergoing a slow reaction to create “chemiluminescence”–or light from chemicals. This reaction is essentially oxidation, the same thing as burning, but the energy released by a chemiluminescent reaction comes out as light, not heat. Indeed, the cool chemistry that takes place inside one of those glowing necklaces is very similar to the chemistry that lets fireflies glow. Here’s How It Works.You start the reaction by bending the flexible tube. This breaks a miniature glass vial inside, and allows two different chemical solutions to mix.