Scientists believe they have captured the elusive "God particle" that gives matter mass and holds the physical fabric of the universe together.
The historic announcement came in a progress report from the Large Hadron Collider (LHC), at CERN.
Professor John Womersley, chief executive of the Science and technology Facilities Council, told reporters at a briefing in London:
They have discovered a particle consistent with the Higgs boson.Discovery is the important word. That is confirmed.It's a momentous day for science
The Higgs boson has been a theoretical particle imagined in 1964 by British physicists Professor Peter Higgs. The Higgs boson is used in the standard theory of particle physics to explain why the universe has mass.
Without the Higgs boson matter would behave as light does and nothing would bind together to form things like the Earth or people.
Finding the Higgs plugs a gaping hole in the Standard Model, the theory that describes all the particles, forces and interactions that make up the universe.
If the particle was shown not to exist, it would have meant tearing up the Standard Model and going back to the drawing board.
In December, LHC scientists revealed they had caught a first tantalising glimpse of the particle.
Since the initial excitement the scientists have sifted through vast quantities of data from innumerable high energy collisions in an effort to reduce the chances of being wrong.
However more work is still needed as the findings need to be verified, although there is only a one in three million chance that they are mistaken.
The next step will be to determine the precise nature of the particle and its significance for our understanding of the universe. Are its properties just as expected for the Higgs boson predicted in 1964, the final missing ingredient in the Standard Model of particle physics? Or is it something more exotic? The Standard Model describes the fundamental particles from which we, and every visible thing in the universe, are made, and the forces acting between them. All the matter that we can see, however, appears to be no more than about 4% of the total. A more exotic version of the Higgs particle could be a bridge to understanding the 96% of the universe that remains obscure.