For a number of years, scientists have been searching for the Higgs Boson, a theoretical sub-particle. They believe that this rarity is really the physical component that gives everything mass. Naturally, locating the particle is not very easy, scientists make use of particle accelerators to smash atoms into each other then they analyse the resulting debris. For years they had not discovered anything; then last year when the CERN researchers made the announcement that they thought they had found it at last.
They have had to retract that announcement now, revealing that the particle was not, indeed, the Higgs Boson.