Extremis

Extremis was developed by Aldrich Killian and Maya Hansen in an attempt to recreate the Super Soldier Serum. Extremis rewrites the operating system of the human body, upgrading strength, speed and durability to the very zenith of human possibility.

Iron Man 3
Dr. Maya Hansen was a research scientist working on a revolutionary process to rewrite genetic codes when she attended a New Year's Eve party in Bern, Switzerland, where she met the rising star inventor Tony Stark. The process could fasten growth and enhance healing, but had the side-effect of causing spontaneous combustions on unstable subjects. Stark left her an equation that could supposedly fix the problems in the formula, but were not fully successful.

After Hansen joined forces with Aldrich Killian and his A.I.M. company, she brought her research with her and eventually the development of her Extremis virus led to her leading a 40-strong team of A.I.M scientists. The downside of Extremis was its explosively unstable nature. Some hosts would accept it, and remain somewhat stable with regular infusions and treatment, while some exploded violently. When Extremis was tested on human subjects a number of them went critical in public, causing Killian to invent a terror plot cover story to keep A.I.M.'s involvement a secret.

Users

 * Aldrich Killian
 * Eric Savin
 * Ellen Brandt
 * Jack Taggart
 * Chad Davis
 * Virginia Potts (unwillingly)

Extremis effects on its subjects
As well as super strength and enhanced agility and reflexes, the user of Extremis is granted incrediblely fast regenerative abilities, being able to regrow whole limbs in seconds, and project massive amounts of heat from their skin, enough to melt metal. It also granted the users super natural durability, with several Extremis users shown only taking minor damage from low caliber firearms.

An unfortunate side-effect is if someone takes too much Extremis, or their body rejects it, they will explode in a blast of heat measuring 3000 degrees Celsius, vaporizing anyone around them.

Aldrich Killian was able to channel the heat and breathe fire.

Trivia

 * The origin and armor of Iron Man used in the 2008 film closely resemble those introduced in "Extremis". Based on his work on "Extremis", artist Adi Granov was brought on as a producer for the film, and he created the final designs for Iron Man's armor.
 * In The Avengers, in order to escape from Loki, Tony uses bracelets as a precursor to the Extremis summoning technology to guide the Mark VII armor to assemble itself onto him as he is in freefall.
 * In the comics version of the virus, it does not allow it users fire based powers.