Cell theory

Understanding of Life - Scientific Contributions timeline

  • 2000 BCE

    Chinese use water microscope

    According to an ancient Chinese text, the Chinese viewed magnified specimens through a lens at the end of a tube, which was filled with varying levels of water according to the degree of magnification they wished to achieve. Thus being the water microscope.
  • 384 BCE

    philosopher Aristotle (Origins of spontaneous generation theory)

    The Greek philosopher Aristotle was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”).
  • 1300

    spectacles were invented

    The art of grinding lenses is developed in Italy and spectacles are made to improve eyesight.
  • Hans and Zacharias Janssen, (Create the first microscope)

    Hans and Zacharias Janssen, (Create the first microscope)
    The earliest microscopes could magnify an object up to 20 or 30 times its normal size.
  • Roughly around the time the telescope was invented

    Historians are not absolutely sure who invented the telescope, but it is known that in 1608 a Dutch spectacle maker, Hans Lipperhey, announced a new lens-based seeing instrument that made distant objects appear much closer.
  • William Harvey (all animals are generated from oviform primordium)

    He denounced spontaneous generation by claiming that even maggots and worms have some origin in eggs. This example is also associated with the establishment of the doctrine ex ovo omnia, meaning that all life originates from an egg, a doctrine that Harvey helped advance.
  • Robert Hooke (First time a cell is observed with microscope)

    The invention of the microscope led to the discovery of the cell by Hooke. While looking at cork, Hooke observed box-shaped structures, which he called “cells” as they reminded him of the cells, or rooms, in monasteries. This discovery led to the development of the classical cell theory
  • Francesco Redi (founder of experimental biology)

    Francesco Redi (founder of experimental biology)
    Francesco Redi demonstrated that the presence of maggots in putrefying meat does not result from spontaneous generation but from eggs lain on the meat by flies
  • Antonie van Leeuwenhoek (Discovered bacteria)

    Anton van Leeuwenhoek uses a simple microscope with only one lens to look at blood, insects and many other objects. He was first to describe cells and bacteria, seen through his very small microscopes with, for the time, extremely good lenses.
  • Antonie van Leeuwenhoek (the observation of sperm cells)

    Antonie van Leeuwenhoek (the observation of sperm cells)
    Antonie van Leeuwenhoek was the first to observe human sperm using a microscope. He described them as being animalcules (little animals), probably due to his belief in preformationism, which thought that each sperm contained a fully formed but small human.
  • John Needham (advocate of the theories of spontaneous generation)

    John Needham challenged Redi's findings by conducting an experiment in which he placed a broth, or “gravy,” into a bottle, heated the bottle to kill anything inside, and then left it open or sealed it (depends on the reports you read). Days later, he reported the presence of life in the broth and announced that life had been created from nonlife. In actuality, he did not heat it long enough to kill all the microbes.
  • Lazzaro Spallanzani

    Spallanzani's results contradicted the findings of Needham: Heated but sealed flasks remained clear, without any signs of spontaneous growth, unless the flasks were subsequently opened to the air. This suggested that microbes were introduced into these flasks from the air.
  • Advancements in microscope technology

    Several technical innovations make microscopes better and easier to handle, which leads to microscopy becoming more and more popular among scientists. An important discovery is that lenses combining two types of glass could reduce the chromatic effect, with its disturbing halos resulting from differences in refraction of light.
  • Joseph Jackson Lister

    Joseph Jackson Lister reduces the problem with spherical aberration by showing that several weak lenses used together at certain distances gave good magnification without blurring the image.
  • Matthias Schleiden

    Concluded that: “All living plants are made of cells”
    Credited for developing first two tenets of cell theory (with Schwann)
    1) All living organisms consist of one or more cells and
    2) The cell is the basic unit of structure for all living organisms.
  • Theodore Schwann

    Concluded that: “All living animals are made of cells”
    Credited for developing first two tenets of cell theory (with Schleiden)
  • Rudolph Virchow

    Concluded that: “Where a cell exists, there must have been a pre-existing cell”
    Credited for developing the third tenet of the cell theory
  • Louis Pasteur

    Louis Pasteur
    In his famous experiment, Louis Pasteur used a swan neck flask. After putting broth in the flask, He then boiled the broth killing any microorganisms which were already present. Then he allowed the infusion to sit.
    If he tipped the flask and allowed the things trapped in the neck to get into the broth then microorganisms began to appear in the broth and multiply rapidly. This demonstrates that microorganisms do not appear as a result of Spontaneous Generation.
  • Friedrich Miescher (Discovered DNA)

    DNA was first identified in the late 1860s by Swiss chemist Friedrich Miescher.
  • Ernst Leitz Company

    addressed a mechanical issue with the introduction of the first revolving turret with no less than five objectives.
  • Louis Pasteur

    at the request of the emperor of France, Napoleon III, Pasteur studied wine contamination and showed it to be caused by microbes. To prevent contamination, Pasteur used a simple procedure: he heated the wine to 50–60 °C (120–140 °F), a process now known universally as pasteurization.
  • Ernst Abbe

    Ernst Abbe formulates a mathematical theory correlating resolution to the wavelength of light. Abbe’s formula makes calculations of maximum resolution in microscopes possible.
  • Walter Fleming

    Walter Fleming discovered cell mitosis and chromosomes, an achievement recognized as one of the 100 most important scientific achievements of all time.
  • Microtomes

    the first microtomes began to be used that enabled significantly thinner samples to be prepared in order to improve sample.
  • Robert Koch

    Robert Koch discovered his famous or infamous postulates: the anthrax bacillus, the tuberculosis bacillus and the cholera vibrio.
  • August Kohler

    August Kohler figured out an unparalleled illumination system that is still known as Kohler illumination. Using double diaphragms, the system provides triple benefits of a uniformly illuminated specimen, a bright image and minimal glare. In other words, Kohler achieved an almost perfect image.
  • Richard Zsigmondy

    Richard Zsigmondy develops the ultra-microscope and is able to study objects below the wavelength of light.
  • Frits Zernike

    Frits Zernike invents the phase-contrast microscope that allows the study of colourless and transparent biological materials.
  • Edouard Chatton (The classification of the two major cell groups)

    The Prokaryote/Eukaryote nomenclature had been proposed by Chatton in 1937 to classify living organisms into two major groups: prokaryotes (bacteria) and eukaryotes (organisms with nucleated cells).
  • Ernst Ruska

    Ernst Ruska develops the electron microscope. The ability to use electrons in microscopy greatly improves the resolution and greatly expands the borders of exploration.
  • Stanley Miller and Harold Urey (explored the question of where and how did life originate?)

    Stanley Miller and Harold Urey (explored the question of where and how did life originate?)
    Miller and Urey simulated hypothetical conditions present on the early Earth in order to test what kind of environment would be needed to allow life to begin. The experiment is considered the classic experiment on the origin of life.
  • Lynn Margulis (how life evolved to multicellular life?)

    Biologist Lynn Margulis first made the case for the endosymbiont theory of mitochondria and chloroplasts.
    as well, Margulis develops a theory for the origin of complex cells that have enclosed nuclei, called eukaryotic cells.
  • Gerd Binnig and Heinrich Rohrer

    Gerd Binnig and Heinrich Rohrer invent the scanning tunneling microscope that gives three-dimensional images of objects down to the atomic level.