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Robert Hooke
In about 1665 Robert Hooke was started to discover the cell theory. He discovered "cells". He discovered that they existed. He did this by looking at a cork slice under a primitive microscope and seeing the dead cell walls of it. He call the compartments inside the dead walls cells. This was better than the previous model because there is no previous model. something is also better than nothing. http://www.softschools.com/timelines/cell_theory_timeline/96/ -
Anton van Leeuwenhoek
Leeuwenhoek discovered single cell organisms which were bacteria. He discovered this by examining a pond water with the 270x microscope which he also discovered. He also discovered the existence of sperm in mammals. This is an advance to the cell theory because nobody know that an organism could only have one cell http://study.com/academy/lesson/anton-van-leeuwenhoek-biography-cell-theory-discoveries.html -
Robert Brown
Robert Brown contribution to the cell theory was that he discovered the nucleus of a plant cell. The nucleus is heart and main part of cell. This is an advancement to the cell theory because people didn't know about the nucleus http://www.softschools.com/timelines/cell_theory_timeline/96/ -
Theodor Schawan
He and Schleiden both made/discovered parts 1 and 2 of the cell theory. Schwann discovered that all animals or made of cells.he discovered this with a microscope. This and Schleiden discovery made part 1 of the cell theory which is the all living things are made of one or more cell. This is an advancement to the cell theory because technically there was no cell theory before this. http://www.encyclopedia.com/people/science-and-technology/cell-biology-biographies/theodor-schwann -
Mattias Schleiden
He discovered that all plants are made of cells.him and Schwann created part 2 of the cell theory together .Which that cell are the basic building blocks of life. He discovered this with a microscope. This was the beginning of the cell theory that is why it better then the preivous http://www.softschools.com/timelines/cell_theory_timeline/96/ -
Rudolf Virchow
Rudolf Virchow's contribution to the cell theory was that he discovered that cells can only come from other cells. He made part 3 of the cell theory. which is that all cell come from preexisting cell. He did this through research as chair of pathological anatomy at the University of Wurzburg. This was an advancement because it added to the cell theory. https://www.reference.com/science/rudolf-virchow-s-contribution-cell-theory-3772dc469526660#