Toxins are poisonous materials that interfere with vital metabolic processes to sicken or kill living organisms. Toxins can be either general poisons that kill many types of cells and organisms, or they can be extremely specific in their target and mode of action. Some are extremely reactive and can be lethal even in very dilute concentrations. Ricin, for instance, is a protein found in castor beans, and is one of the most toxic organic compounds known. Three hundred picograms (trillionths of a gram) injected intravenously is enough to kill an average mouse. That means that a few teaspoonsful of this substance, if divided and delivered in individual doses, could potentially kill all the mice in the world. Put another way, an amount of supertoxins that is invisible to the naked eye, if delivered in the right way, could be lethal.

An important principle of toxicology (the...