Cells & Transport Study Guide Cell Theory 1) All living things are made up of cells 2) Cells are the basic units of structure and function in an organism 3) New cells are produced from existing cells Scientists: 1665 Robert Hooke Coined word ?cell? Looked at cork under microscope 1674 Anton van Leeuwenhoek Perfected the simple microscope Discovered protozoa 1838 Matthias Schleiden Discovered/published fact that all plants are made of cells 1839 Theodor Schwann Discovered/published fact that all animals are made of cells 1855 Rudolf Virchow Discovered/published fact that all cells come from preexisting cells 1931 Janet Plowe Demonstrated that a cell is a physical structure 1970 Lynne Margulis Created endosymbiotic theory Endosymbiotic Theory