Particle accelerators are a major invention of the 20th century. In the last eight decades, they have evolved enormously and have fundamentally changed the way we live, think and work.There are also tens of thousands of small accelerators all over the world. They are used every day for medical imaging, cancer therapy, radioisotope production, high-density chip-making, mass spectrometry, cargo x-ray/gamma-ray imaging, detection of explosives, illicit drugs and weapons.