In Gaia, planet of Final Fantasy VII, a mysterous substance known as Mako flourishes in underground reservoirs in a massive, single unified Lifestream. The Shinra Corporation established Mako Reactors used to convert the Mako into electrical energy, using a processing method that all but wasted the massive power Mako is capable of bringing. Naturally, reckless use of resources has consequences, and in areas where Reactors had been established, plantlife withered and animal life vanished or mutated horrifically; Midgar alone is a prime example, while leaks could lead to massive development, leading to unnaturally strong predators springing forth; Nibelheim is an example of this. These reactors were established thus; eight in Midgar, Shinra's prideful citadel, one in Fort Condor, one in Junon, Shinra's military depots, one in Nibelheim, and one formerly was installed upon Gongaga before a rebel faction blew it up.
What very few realized was that Mako is, in reality, the planet's lifeblood, that allows life to spring forth from the Earth and grow; without Mako nothing ever grows in Gaia. The major Mako concentrations were presented in places where the Planet had suffered severe injuries and thus wished to heal itself by gathering as much lifeblood as possible. The Shinra executives sought the mythical Promised Land believing it was a land ripe with powerful Mako, while Avalanche instead tried to destroy as many reactors as they could to aid the planet's recovery. In the Sephiroth Conflict, the seven operational Mako Reactors were used to fuel the company's massive superlaser, the Sister Ray, to destroy the biomechanical sentries of the Planet, the Weapons, and shatter Sephiroth's protective shell over the Northern Crater. Professor Hojo attempted to once again fire the weapon to lend more Mako power to Sephiroth, but was defeated and killed. Upon the Jenova War, the Lifestream played a key role by aiding Holy in deflecting Meteor. By doing this, the citizens of the above world realized the importance of Mako and how Shinra had squandered that power in electrical power. Thus, Shinra was forced to cease all operations in all reactors soon after.
Later, when the Deepground group attempted to fool the Lifestream into fleeing into space with the aid of the massive weapons station Omega, the eight Midgar Mako reactors were used as conduits to draw the Lifestream into Omega and speed the planet's death.
Overfilling a human's system with Mako ends up often with "Mako poisoning" in which the subject is unable to cope with the excess energy and often goes insane. Monsters often grow in size and aggressiveness. However, controlled processes are able to produce supersoldiers, a process Shinra briefly mastered to create its inner army.