Arc Reactor Technology
Arc Reactors are a form of super-efficient non-poluting nuclear reactor, originally invented by Howard Stark and Ivan Vanko in the late 1940s. Industrial models use a plutonium core, however due to Plutonium's toxicity, later iterations of Tony Stark's medical reactor used a core of JARVium.
Despite their efficiency, the cost of manufacture was prohibitively expensive, and after building the reactor which still powers Stark Industries HQ Howard Stark did not build any more.
Duing Tony Stark's inprisonment by the Ten Rings, he was able to miniturise the technoligy, which he used to power the electro-magnet Ho Yinsen had embedded in his chest in an attempt to save his life.
The miniturised reactor generated power at a far higher rate than was needed to power the reactor, and this excess power was used to power early version of the Iron Man Suits. Later iteractions, and the War Machine Armour, had independant arc reactors built into the suits themselves.
Stark's experiments in miniturisation also lead to breakthroughs in terms of both efficiency and cost of production, and Arc Reactors were used to power a number of instilations, including Stark Tower.