-
Zacharias Janssen
He invented the compound optical microscope (a microscope made with two eyepieces with one lens each to allow for binocular vision). It made the observation of small structures easier and more efficient. -
Robert Hooke
Hooke created a magnified microscope with a zoom of 50x and used this to observe thin slices of cork. Within these slices, he found empty cavities which he named cells (for the cells of a monastery). He was unsure of their function. -
Anton van Leeuwenhoek
Leeuwenhoek learned to grind lenses and then made his own microscope (magnification of 270x which was much greater than Hooke's). He was the first to observe living, one-celled organisms(and also discovered bacteria). He called these living things animalcules, which are now known as microorganisms. -
Mathias Schleiden
Schleiden proposed that all plant tissues are composed of cells. He also reached the conclusion that cells are the basic building blocks of life and had the first generalized statement on cells. -
Theodar Schwann
He stated that not only plant tissue, but also animal tissue, is made of cells. Schwann is also well known for the first statement of the cell theory (which contains two out of the three main points of the modern theory):
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 -
Rufolf Virchow
Virchow added the third part of the cell theory that states: all cells develop only from existing cells. On the same note, he also stated that all living things come from other living things. This statement contradicted the previously thought to be correct idea of spontaneous generation. -
Louis Pasteur
Pasteur disproved spontaneous generation, proving that cells can only form from pre-existing cells. He did this through an experiment with two flasks of broth, only one of which was exposed to the air and dust within it (where microorganisms can lie). The flask exposed turned murky, signaling life, while the sealed one remained clear. He's also credited for discovering that diseases can be spread by bacteria.