There are many different experiments that can provide different information about the composition of matter, in different ways and with different conclusions. Here I will look at the discovery of the electron, how our understanding of it has changed over the years, and measure how it has contributed to where we are today.Joseph John Thomson (JJ Thomson, 1856 - 1940) is widely recognized as the discoverer of the electron. Thomson was professor of experimental physics at Cambridge University and director of its Cavendish laboratory, from 1884 to 1919. It was here that his best-known, most varied and most comprehensive work in the field of the conduction of electricity within gases was undertaken . . In 1897 Thompson made an announcement stating that cathode rays were negatively charged particles which he referred to as "corpuscles" and stated that they had a mass about 1,000 times less than that of a hydrogen atom. Thompson proposed that corpuscles were the elements from which atoms were built and concluded that cathode rays possessed a new state in their ability to transport beyond the ordinary gaseous state. This has been proposed as a state in which all matter derives from different sources, such as hydrogen or oxygen. This implied that the original discovery was different from that now proposed by Thompson, that particles were a fundamental building block of all matter. Thompson's experiment used a pair of plates as electrodes in a glass tube, between which a high voltage potential was applied. When the gas pressure in the tube became very low (less than 0.1 atmosphere), an electrical discharge occurred. This was called vacuum exhaust. When the gas pressure in the pipe is further reduced... half of the paper... situation. We would lack an understanding of the anatomy of atoms, how they are made up of a nucleus with surrounding electrons, the influence they have on the world around us and how it works. The importance of electrons would not be appreciated, nor their relevance for experiments on the theory of matter. Works Cited1) Anthony Carpi, Ph.D. "Atomic Theory I: The Early Days", Visionlearning vol. CHE-1 (2), 2003.2) JJ Thomson (1897), Cathode Rays, Philosophical Magazine, 44, 293 — The classical measurement of the mass and charge of the electron3) Thomson, George Paget. (1964) JJ Thomson: The discoverer of the electron. Great Britain: Thomas Nelson & Sons, Ltd.4) Navarro, Jaume, 2005, "Thomson on the Nature of Matter: Corpuscles and the Continuum", Centaurus 47(4): 259-82.5) Nobel Lectures, Chemistry 1901-1921, Elsevier Publishing House, Amsterdam, 1966