Glow sticks, like those brandished by trick-or-treaters and partygoers, light up due to excited electrons of the molecules in the contained fluorescent dye. Electrons accept the exciting energy from a chemical reaction that results when an inner tube in the glow stick is cracked and two fluids come into contact. After exciting to a higher energy level, they relax back to a lower energy by releasing light that can guide young candy hunters in costumes.