Scientists may have spotted the most sought-after prize in particle physics, the elusive Higgs particle.
Finding the Higgs is vitally important for our understanding of the way the Universe is made as it is the particle that gives matter its mass.
"We all hope that what we are seeing is the Higgs on the horizon," said Dr Chris Tully of Princeton University to a packed Cern auditorium.
Hundreds of particle physicists heard that all four experiments at the Large Electron Positron (Lep) collider had found the first hints of the elusive Higgs boson.
The atom-smasher that produced these events is scheduled to close down in a few weeks, meaning that researchers have little time to confirm their discovery.
Unseen sea
Predicted over 30 years ago, the Higgs particle gives other particles such as electrons their mass. In a sense, other particles are swimming through a sea of unseen Higgs bosons, which cause a drag that shows itself as mass.
The hunt for the Higgs has been on for over a decade.
Fast-moving sub-atomic particles have to be smashed together to detect it. If they are lucky, physicists may be able to see evidence of the Higgs in the debris from the collision.
Such a Higgs signature may have been seen in several unusual events observed recently at Lep. It is possible that what has been seen is due to chance, and hence more observations are required.
The excitement about the Higgs may spur Cern's rival, Fermilab near Chicago, to intensify its efforts to find the Higgs. Fermilab will resume experiments later this month.
The committee that decides Cern's research programme will decide next week whether the Lep accelerator will continue running until December. Particle physicists nervously await its decision.