He was born in Greece, 460BC. He was a philosopher. Democritus studied about mathematics, biology, geography, astrology, economy and sociology. He had an idea what is the smallest piece of matter. Democritus thought if you continue cut the stone into smaller pieces, at one point you can’t cut because it is too small. He called that piece “atomos”, meaning “indivisible”. For him, atomos can not be divisible or destroyed. However, Democritus did not do any experiments. Democritus was the first person that used the word atom. He died in 360BC.John Dalton: John Dalton was born on 6th of September 1766, in Eaglesfield, England. He was meterologist, chemist and physicist. He had an atomic theory. He said all matter is made up of tiny particles called atoms, all atoms of a given element are similar to one another and different from atoms of other elements, atoms of two or more different elements combine to form compounds. A particular compound is always has the same number of each kind of atom and atoms are never created or destroyed during a chemical reaction. He based his theory with more on experimentation than pure reason. That’s why he was different from Democritus. He also studied about “colour blindness” the illness which known “Daltonism”. He found a law of conservation of mass. He died on July 27, 1844 Manchester, England.Joseph John Thomson: Joseph John Thomson was born in Cheetham Hill on December 18, 1856. J.J. Thomson graduated from Owens College. He was a professor on Cambridge University. In 1897, J. J. He applied electricity to a glass tube, which produced streams of small particles called cathode rays Because these rays were attracted to a positively charged electrode, Thomson realized that the particles in rays must be negatively charged. So he discovered the electrons by using Cathode Ray Tube. J. J Thomson called electrons corpuscles. He published “Application of Dynamics to Physics and Chemistry” “Elements of the Mathematical Theory of Electricity and Magnetism.” and “Notes on Recent Researches in Electricity and Magnetism”, He had an atomic model which known “Thomson’s Plum Pudding Model”. It proposed in 1904. He was selected Royal Society in 1884. He published lots of books and won a lot of prizes. In 1906, he received Noble Prize. Thomson died on August 30, 1940.