H₂O₂--a molecule of two hydrogen atoms and two oxygen atoms. It decays into water (H₂O) and oxygen (O₂) when exposed to energy in the form of heat or light. It is a powerful oxidizing agent, and is sold diluted with water. It is used in low concentrations as a disinfectant (Halcyon--I was waiting for someone to point out that out. I don't use hydrogen peroxide myself. I find it amusing that various websites recommend bathing in it to "restore," "rejuvenate," and "refresh" the body), to "bleach" hair, and in higher concentrations for various industrial and environmental uses.

Its one of those many household chemicals that everyone should have vast quantities of in their cabinet for divers and sundry purposes.