The basic conception of a subject now known as Subatomic Particle physics dates back to 500 BC when the Greek philosopher Leucippus and his pupil Democritus suggested that matter consists of small, indivisible particles, which they called atoms. For more than 2000 years after this, the notion of atoms lay in obscurity. For quite a long time, people believed that all matter consisted of four elements: earth, fire, air, and water. We now know that atoms do exist, and that some particles smaller than atoms also exist.