Cell Theory Development

  • Hans and Zacharias Janssen

    Both lens makers, invented the microscope using two lenses. First "compound" light microscope (more than one lens).
  • Robert Hooke

    Used a compound light microscope that had three lenses. His curiousity was piqued by the properties of cork and why it floated. He saw the air chambers and called them "cells".
  • Antoni van Leeuwenhoek

    Was the first to see movement of free-living cells that were their own individual systems. Named these "animalcules".
  • Francesco Redi

    Questioned spontaneous generation, which was accepted at the time. If you left raw meat out, maggots would "spontaneously" appear. He conducted an experiment with pieces of meat in three containers: one completely open and exposed to the environment, another with gauze fastened over the opening, and the last sealed with a lid. Flies swarmed the first and second, however the only one that developed maggots was the first one. Yet his evidence didn't affect the validity of spontaneous generation.
  • John Needham

    Wanting to prove that life could be produced from something non-living, Needham conducted an experiment with chicken broth. At this time, it was believed that boiling something killed micro-organisms. However, micro-organisms still appeared. He suggested there was a "life force" that aided spontaneous generation. Lazzaro Spallanzani, Italian priest and scientist, disagreed. He believed there were micro-organisms in the air.
  • Robert Brown

    He identified an important cell structure, the nucleus, while studying orchids. Although others had seen it, he was the first to put emphasis on its importance.
  • M. J. Schleiden and Theodor Schwann

    Schleiden believed that the nucleus did in fact affect the development of the rest of the cell structure. He discussed this with his friend Schwann, who was studying animal physiology. He recognized these opaque spots in animal cells as well. Together, they proposed that all plants and animals were composed of cells and cells were the basic unit of all organisms.
  • Louis Pasteur

    A submission to the French Academy of Sciences changed the common belief of spontaneous generation. He boiled meat broth except he did it in a flask with an S-shaped neck, where the micro-organisms got trapped. This broth did not spoil. However, when he tipped it, it did, having gained contact with the micro-organisms. We still use this method today (pasteurization).