1. Cell Theory Scientists

2. Robert Hooke Who: Robert C. Hooke When: 1653 Consignment from the King, Personal curiosity Methods: Looked at a thin slice of cork through a microscope at 50x Institution: The Royal Society Where: London, England Funding: King Charles III Technology: Microscope

3. Robert Hooke Robert C. Hooke (1635-1703) was 26 years old when he joined the Royal Society For Scientists. A self-educated child prodigy, he showed technical aptitude by recreating the entire inner workings of a clock out of wood, then assembling it to run. Hooke also taught himself technical drawing, a skill he used to capture observations through his microscope. Hooke went beyond his commission and looked at everything from fabric, leaves, mica, glass, flint, and even frozen urine. When Hooke viewed a thin cutting of cork he discovered empty spaces contained by walls, and termed them pores, or cells. The term cells stuck and Hooke gained credit for discovering the building blocks of all life. Hooke viewed a thin cutting of cork and discovered empty spaces contained by walls which he termed cells.

4. Matthias Schleiden Who: Matthias Schleiden When: 1838 Methods: Drawing upon published information Institution: University of Berlin Where: Berlin, Germany

5. Matthias Schleiden Matthias Jakob Schleiden, a German botanist, concluded that all plant tissues are composed of cells and that a plant arose from a single cell. He declared that the cell is the basic building block of all plant matter. This statement of Schleiden was the first generalizations concerning cells. Born in Hamburg and educated in law at Heidelberg, Schleiden left law practice to study botany, which he then taught at the University of Jena from 1839 to 1862. Schlieden investigated plants microscopically and conceived that plants were made up of recognizable units, or cells. Plant growth, he stated in 1837, came about through the production of new cells, which, he speculated, where created from the nuclei of old cells. Although later discoveries proved him wrong about the role of the nucleus in mitosis, or cell division, his conception of the cell as the common structural unit of plants had the profound effect of shifting scientific attention to living processes as they happened on the cellular level-a change that initiated the field of embryology. A year after Schleiden published his cell theory on plants, his friend Schwann extended it to animals, thereby bringing botany and zoology together under one unifying theory.

6. Theodor Schwann Who: Theodor Schwann When: 1839 Methods: Drawing upon published information Institution: University of Berlin Where: Berlin, Germany

7. Theodor Schwann Theodor Schwann, a German biologist, reached the same conclusion as Schleiden about animal tissue being composed of cells, ending speculations that plants and animals were fundamentally different in structure. Schwann described cellular structures in animal cartilage. He pulled existing observations together into theory that stated: 1. Cells are organisms and all organisms consist of one or more cells. 2. The cell is the basic unit of structure for all organisms and that plants and animals consist of combinations of these organisms which are arranged in accordance with definite rules. In other words, the cell is the basic unit of life. This statement was the second generalization concerning cells and is the most important in the development of biology. It became known as the cell theory. Schwann applied the cell theory of the German botanist Matthias Jakob Schleiden to the evolution of animal life. He also demonstrated that the mature tissues of all animals are traceable to single cells.

8. Rudolf Virchow Who: Rudolf Virchow When: 1858 Why: To advocate and popularize the theory that all cells form from other cells Methods: Drawing upon published information Institution: University of Berlin Where: Berlin, Germany

9. Rudolf Virchow Virchow was a man who worn many hats. He was a doctor, anthropologist, pathologist, biologist and politician. Virchow was from a farming family, he studied medicine and chemistry in Berlin at the Prussian Military Academy. In 1845, while working as an intern alongside Robert Froriep, Virchow published his first scientific paper. Unlike his German peers, Virchow felt that clinical observation, animal experimentation to determine causes of diseases, especially at the microscopic level, were the basic principles of investigation in medical sciences. He thought the cell was the basic unit of the body that had to be studied to understand disease. Virchow's most widely known contribution was his development on cell theory. He was cited for being the first to recognize leukemia cells and that all cells came from pre-existing cells. At first Virchow did not believe the evidence for cell division, that it only occurs in certain types of cells. Rudolph Virchow proposed the third and final part of cell theory, and in completion of the puzzle, he received the Copley Medal in 1892.

10. Cell Theory Timeline