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330 BCE
Aristotle
Originated the theory that an organism develops gradually form undifferentiated material, later called embryos. -
Zacharias Janssen
He created the first optical microscope. -
Jan Baptist van Helmont
Partially discovered the process of photosynthesis. -
Robert Hooke
He was the first to observe cells under a microscope and named cells. He said they looked like small rooms. -
Antoni van Leeuwenhoek
He learned to grind lenses and assemble them into simple microscopes. He also reported that he had observed "little animals" (protozoa) while looking through a microscope. -
Lorenz Oken
He maintained that all organic beings originate from and consist of vesicles or cells. -
Robert Brown
He discovered the nucleus in the cell and discovered the continuous motion of particles in a solution, which he later called Brownian Motion. -
Matthias Schleiden
The first to discover that all plant tissues are composed of cells and that an embryonic plant arose from a single cell. He declared that the cell is the basic building block of all plant matter. -
Theodor Schwann
Published a book that included the first statement of cell theory: all living things are made up of cells. He was also considered a founder of cell theory. -
Albrecht von Roelliker
He discovered that sperm cells and egg cells are also cells. He also helped confirm that cells come from pre-existing cells and added the idea that tissue should be studied and understood as a mass of individual cells. -
Rudolf Virchow
Proposed the idea that all living cells must arise from pre-existing cells. -
Louis Pasteur
Disproved the idea of spontaneous generation with an experiment that firmly established cell theory beyond doubt and solidified the basic steps of the scientific method. -
George Palade
Discovered previously unknown organelles in the cell, ribosomes, where the cell's formation of proteins takes place. He also identified the paths proteins take through the cell.