Inside glow-sticks there are actually two chemicals. The glowing comes from a reaction that occurs when the two chemicals mix together. The chemicals mix when you 'crack' the glow stick. Glow sticks come in different colors and the color they are depends upon a dye. Usually in the glow sticks that you see one chemical is hydrogen peroxide (maybe you put this on your cuts to clean them it fizzes and turns white). The other chemical is usually what is called an ester. These two chemicals mix together, then interact with the dye causing the glow.