Most people think that the study of elementary particles is a relatively new branch of physics.
THIS IS NOT SO!
The notion that matter is made up of invisibly small INDIVISIBLE particles was first documented in the 5th century BC! At that time, most great scientists were also the great philosophers of the day. A wise old man named Leucippus called the elementary constituents of matter ATOMOS, which means "indivisible". Unfortunately, the ideas of Leucippus and his famous pupil Democritus were rejected by the other great philosophers of their day... So we don't really remember them as the first great particle physicists...(we all know what Democritus went to work on after he stopped working with particles!) But the ancient Greeks did believe that all matter was made up of 4 basics constituents:
In the 1800's Mendeleyev summarized what we know as basic constituents of matter as the atoms of chemical elements in the PERIODIC TABLE. At that time, there were many basic constituents of matter.
By the 1930's we thought that all the world was composed of 3 basic types of matter:
And these days, in the 1990's we can explain everything we see around us in terms of quarks and leptons.
In particle physics, we want to KNOW EVERYTHING about the world around us:
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Look below to check into some current particle physics experiments...
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BaBar Experiment at the Stanford Linear Accelerator Center
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CERN and OPAL 
The OPAL Experiment at CERN (the European Laboratory for Research in Particle Physics)
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Tell me what you think about Particle Physics:janis@physics.ubc.ca