Created by a team under the leadership of Dr. Carol Marcus, the Genesis effect is a method of reorganizing the molecular structure of matter at a subatomic level with life generating results.
Dr. Marcus planned to carry out the project in three stages. Her team successfully achieved stage one within a laboratory prior to 2284. Stage two was planned to take place underground on a lifeless planetoid, and once the Federation granted approval the Regula asteroid was chosen. A space laboratory, Regula I, was orbited around the planetoid and a Starfleet engineering team spent ten months in spacesuits tunnelling out a test site. After a year of development work the team proceeded with the second phase test. The stunning potential of the device became clear; within the space of a day it hollowed out an underground cave several cubic kilometres in size. Lifeforms rapidly developed within the cave, creating an entire ecosystem from scratch.1
Starfleet assigned the USS Reliant to the project in order to find a test site for phase three of the project. Dr. Marcus planned to try the process on a planetary scale, and set out to build a torpedo-like Genesis device which would be launched at a lifeless moon or other body. The detonation would begin a chain reaction that would rapidly spread across the entire surface, turning a dead world into a living breathing planet capable of sustaining whatever life forms were deposited on it.
Unfortunately, the effect would 'overwrite' any existing life with the new matrix. Aware of the awesome weapons potential of this technology, Dr. Marcus was determined to prevent the test from killing so much as a single microbe. The Reliant was tasked with finding a completely lifeless planet for the stage three test.
Unfortunately, whilst investigating Ceti Alpha V the Reliant was captured by Khan Sing, marooned there by Captain Kirk many years earlier. Khan coerced the crew into revealing the existence of the Genesis project and immediately attempted to capture the device. He was ultimately successful in doing this, but Kirk and the Enterprise lured the Reliant into the Motarra nebula near Regula and crippled it there.
In a last attempt to destroy Kirk, Khan detonated the Genesis device within the nebula. The device performed beyond any previous expectations, completely destroying the nebula and using the matter to create a new planet entirely from scratch. As with the Genesis cave, lifeforms evolved on the planet within a matter of days.1
Amazingly, the Starfleet team led by Dr David Marcus - son of the project leader - which went to investigate the planet also discovered that the effect had also regenerated the body of Captain Spock, which had been fired onto the planet after his death. Like the stage two cave on Regula, the Genesis planet itself had a fully developed ecosystem on its surface. It also had an amazingly diverse surface, with every variety of land and weather known to Earth within a few hours walk.
Aware of the Genesis device's potential as a weapon, the Klingons were working to uncover its secrets almost as soon as Khan detonated it. They managed to obtain the original project proposal made by Dr. Marcus, and sent a Bird of Prey to the Genesis planet to capture the technology itself if possible. The ship destroyed the Grissom and captured the landing party led by Dr. Marcus.2
It had become clear during the investigation that there was something badly wrong with the planet. Dr. Marcus confessed that he had included protomatter in the device, an unstable substance that had been condemned by every ethical scientist and banned from use. Its presence in the matrix rendered the resulting planet unstable and caused it to ageing at a rapid pace.
Captain Kirk, acting in violation of orders, arrived at the planet only to see the Enterprise disabled and boarded by the Klingons. He destroyed the ship and managed to capture the Klingon vessel, escaping the Genesis planet as it tore itself apart.2
Despite almost a century of research, the Genesis device never proved fully successful. However, while it cannot create habitable planets it remains a highly effective weapon of mass destruction. Fortunately, the Federation has never employed such methods and the technology remains unused.