The Large Electron and Positron collider at CERN. Started operation in 1989. With its 27 km circumference it is the world's longest accelerator. Its task is to study the weak force. Using the LEP, scientists have found three families of particles that are thought to make up all matter. Over the past few years the LEP's energy has gradually been increased reaching climax at 202MeV in August 1999, just a few months before the last season shutdown. Technicians will start dismantling it at the end of the year 2000 to make room for the LHC.