Any person even remotely familiar with Superman lore has heard of this superhero's number-one vulnerability: kryptonite.
First introduced on the Superman radio show in 1945 before making its way into the comic-book pages of Superman #61 (1949), kryptonite is used in the Superman mythology to denote any portion of material that survived from Superman's exploded planet, Krypton. The material, described as
the only thing the Man of Steel has to fear in the entire universe in Action Comics #291 (1962), scattered throughout space and
laden with cosmic energy, emits a deadly radiation to which Superman and other surviving natives of Krypton are vulnerable. Because kryptonite fragments still float in space, they make their way to planet Earth buried in meteors.
There are five unique types of this planetary matter, the nuances of which only the most die-hard Superman fan has committed to memory. Green kryptonite, the most common variety and the one traditionally discussed in comics stories of the Golden (1938–1954) and Silver (1956–1969) Ages, is the only type potentially fatal to the hero. If not removed
in time from Superman's midst, death follows the loss of his superpowers and a general state of inertia. While large quantities produce the most drastic effects, even a piece the size of a jawbreaker can bring Superman to his knees. Though the Man of Steel has often circumvented the effects of green kryptonite by using the heat of his X-ray vision to melt away small chunks of the substance, this Super-plan-of-attack doesn't work with larger quantities.
Though not fatal, red kryptonite imposes temporary (usually twenty-four hours), strange, and random results, such as when it turned Superman into a giant ant, drove him insane for forty-eight hours, or made it impossible for him to write or speak in any language other than his native Kryptonese. As a general rule, once Superman is exposed to the strange effect, he becomes immune to it, forcing his writers to come up with new and interesting ways of afflicting the hero. Gold kryptonite permanently steals Superman's superpowers; white kryptonite affects only plant life; and blue kryptonite is hazardous only to Bizarro (a Superman
replica hero built by supervillain Lex Luthor as
a grotesque imitation of Superman in Action Comics #254 in 1959) and related Bizarro creatures. Kryptonite of the green, red, and gold variety is toxic to any surviving natives of Krypton, including members of the Superman family such as Supergirl and Krypto the Super-Dog.
Over the years Superman writers introduced variations like jewel kryptonite and X-kryptonite, the latter of which gave Supergirl's cat Streaky superpowers. The one substance impervious to kryptonite is lead. In 1971, Superman editor Julius Schwartz excised kryptonite from the Man of Steel's canon, although it has been used more judiciously since the reworking of the Superman mythos beginning in The Man of Steel #1 (1986). The glowing substance from a distant planet factors heavily into Superman media, having been used in the 1948 movie serial Superman, a half dozen episodes of the Superman television series of the 1950s, animated cartoons of the 1960s and 1970s, and the four live-action Superman films of the late 1970s and 1980s.