How do glow sticks work
Glow sticks! 
These multi color glowing goodies are a decades old tradition now at fairs, festivals, parties and are seen by the millions around the world during Halloween celebrations. They are used to illuminate trick or treaters as both a celebratory feature, and more importantly as a safety device to make them visible in the dark to oncoming traffic. Also known as light sticks they are also used by divers, spelunkers or cave explorers, accident safety responders and emergency officials.
So what makes them glow? It is a simple chemical reaction. There are three components of a glow stick. There need to be two chemicals that interact to release energy and also a fluorescent dye to accept this energy and convert it into light. Although there is more than one recipe for a, a common commercial glow stick uses a solution of hydrogen peroxide that is kept separate from a solution of a phenyl oxalate ester together with a fluorescent dye. The color of the dye is what determines the resulting color of the stick when the chemical solutions are mixed. The basic premise of the reaction is that the reaction between the two chemicals releases enough energy to excite the electrons in the fluorescent dye. This causes the electrons to jump to a higher energy level and then fall back down and release light.
Most recently they are now being used in the medical field in the form of illuminated portable intubation tubes, so from toys to saving lives these have turned out to be a pretty serious invention originating 25 years ago!
Also, see this cool video explaining how they work! How do glow sticks work-video.