Compare and contrast the traditional cell theory with the modern cell theory.

As technology began to advance during the Renaissance, scientists' ability to look more closely at living organisms brought us classical cell theory. By 1855, the three basic parts were in place. They are that all living things are composed of cells, cells are the basic units of structure and function in living things, and that all cells are produced from other cells.

There were several major advances that changed in the three centuries leading up to this. In 1663, Robert Hooke observed small, boxlike structures when he looked at cork under an early compound microscope. He did not know their structure or function, and as he was looking at dead, dried samples did not see any organelles. Anton von Leewenhoek observed living, unicellular organisms in 1674. In the 1850s Schleiden, Schwann, and Virchow added that animals and plants are made of cells, and that cells arise from other living cells.

Modern cell theory builds on the previous three components; it does not eliminate any of the earlier information. Modern cell theory adds that energy flows within cells, hereditary information is passed on from cell to cell, and that all cells have the same basic chemical composition. Major advances in technology in chemical analysis, DNA technology and microscopy have added to our information about cells.