Janssen’s invention of the microscope , with the aid of his father Hans, allowed English scientist Robert Hooke to use a primitive microscope to view the cell walls of a piece of cork in 1663.
The cell was discovered by Robert Hooke in 1665. He examined very thin slices of cork and saw a multitude of tiny pores that he remarked looked like the walled compartments a monk would live in. Because of this association, Hooke called them cells, the name they still bear. However, Hooke did not know their real structure or function. Hooke's description of these cells was published in Micrographia. His cell observations gave no indication of the nucleus and other organelles found in most living cells.
Anton van Leeuwenhoek was inspired by the glasses used by drapers to inspect the quality of cloth. He taught himself new methods for grinding and polishing tiny lenses of great curvature which gave magnifications up to 270x diameters, the finest known at that time.
These lenses led to the building of Anton Van Leeuwenhoek's microscopes considered the first practical microscopes, and the biological discoveries for which he is famous. Anton Van Leeuwenhoek was the first to see and describe bacteria (1674), yeast plants, the teeming life in a drop of water, and the circulation of blood corpuscles in capillaries. During a long life he used his lenses to make pioneer studies on an extraordinary variety of things, both living and non-living, and reported his findings
Matthias Schleiden found that all plants are composed of cells, and communicated the finding to Schwann, who had found similar structures in the cells. Other researchers confirmed the similarity, as explained in his book, where he concluded, "All living things are composed of cells and cell products. This became the cell theory
He stated that the different parts of the plant organism are composed of cells. Thus, Schleiden and Schwann became the first to formulate what was then an informal belief as a principle of biology equal in importance to the atomic theory of chemistry. He also recognized the importance of the cell nucleus, and sensed its connection with cell division..
Rudolph Virchow suggested that all cells come from pre-existing cells. His aphorism'omnis cellula e cellula' meaning every cell from a pre-existing cell became the foundations of division, even if the process was not fully understood then.
He also stated that not all plants are made up of cells,which eventually lead to the creation of the cell theory.