Kironide is a very rare and long-lasting source of great power.
In 2268, the Starship Enterprise arrived at the planet known as Platonius, where the inhabitants had gained extraordinary psychokinetic powers, which they used to entertain themselves by sadistically torturing Alexander, a Platonian who did not have the powers. It was discovered that they had gained their powers due to the kironide that was present in the local vegetation, and that Alexander did not have the powers because he posessed a pituitary deficiency which prevented him from metabolizing the kironide. In order to escape the control of the Platonians, Doctor McCoy injected Captain Kirk and Commander Spock with a high dose of kironide in order to reproduce the Platonians' powers. Their plan worked and they were soon able to overpower Parmen, the Platonian leader, and gain their and Alexander's freedom. (TOS: "Plato's Stepchildren")