Omega Molecule
The Omega molecule is a short-lived, highly unstable molecule, believed to be the most powerful substance in the known universe. Some Federation cosmologists theorize that Omega existed in nature at the instant of the Big Bang, when the universe as we know it was born.
An Omega molecule would be so energetic that even a few molecules would, in theory, be able to power a whole civilization. The molecule could be synthesized using boronite ore. A single Omega molecule was synthesized in the late 23rd century by Dr. Ketteract, a Federation physicist. The molecule remained stable for a fraction of a second before it exploded, killing 127 leading Federation scientists, destroying the research station and causing ruptures in subspace extending several light years, making warp travel and subspace communications impossible in the region. This region is known as the Lantaru sector, in order to retain secrecy of the cause of the impassibility of the region, all those who travel through it are told it is a natural phenomenon.
Starfleet Command immediately realized that the use of even a few Omega molecules could effectively end spacefaring travel in an entire quadrant or even the entire galaxy. Without subspace, planets and ships would have no way to travel or communicate with others, effectively ending interstellar civilization. The development of warp drive by less advanced nations would also become impossible. In short, the final frontier would be unreachable. Starfleet not only banned research into Omega, but issued the Omega Directive, ordering the destruction of Omega molecules by any means necessary, and the suppression of any knowledge of the particle's existence beyond starship captains and flag officers.
Knowledge of Omega was not restricted to the Federation. The Borg learned of the substance through the assimilation of thirteen species, and were able to synthesize a single molecule of Omega. That molecule also exploded, destroying 29 Borg vessels with 600,000 drones lost. The Borg, who referred to Omega as Particle 010, regarded Omega with near-reverence as they believed it to exist in a flawless state. Because the Borg saw the Omega Molecule as "perfection", all Borg were ordered to assimilate it at any cost. From their data, the Borg designed a harmonic resonance chamber which could theoretically stabilize the molecule.
Another civilization in the Delta Quadrant was actually successful in synthesizing some 200 million Omega molecules in 2374. They were able to keep the molecules stable by using Omega's own resonance frequency to calibrate their containment field, though eventually an accident devastated their research facility. The starship USS Voyager managed to neutralize the molecules before they could do any further damage to subspace. Seven of Nine adapted the Borg harmonic resonance chamber design to emit an inverse frequency which would dissolve Omega's interatomic bonds. A few seconds before Seven's cargo bay would be decompressed to jettison the harmonic resonance chamber into space, the molecules started to stabilize spontaneously. The remaining Omega molecules were destroyed by a modified gravimetric torpedo. Afterwards, in the Da Vinci holodeck program, she said "for 3.2 seconds, I saw perfection." (VOY: "The Omega Directive")