Throughout the 1990s CERN physicists used a particle accelerator called the Large Electron Positron collider, or LEP for short. In electron microscopes, accelerating voltages range from kilovolts to around a Megavolt. At LEP, which was a circular machine, the particles were exposed to an accelerating voltage of up to 3650 Megavolts on each lap.
LEP was a giant underground machine. Its circumference was 27 kilometres and, as its name suggests, it accelerated electrons and their antimatter counterparts, positrons, and then collided them head on. This technique is an alternative to "shining" a beam of particles on a sample to be studied, though that is also done at CERN. Colliding particles maximises the energy available. The resolution achieved with the LEP accelerator is a thousand times smaller than the size of a proton.