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Robert Hooke
Believing strongly in the importance of scientific observation, English scientist Robert Hooke studied the natural world under a microscope (of his own design). In 1665, he had organized and published his findings in a book, the most famous of which was his drawing of a cork sliver, based on which he introduced the idea of cells,—which later became the foundation of new fields biology. -
Anton van Leeuwenhoek
Inspired by Hooke’s published works, amateur scientist Anton van Leeuwenhoek took to studying the microscopic world with simple microscopes of his own design. With this, he was able to make his own observations and find evidence proving the existence of “…little living animacules, very prettily a-moving.” These “animalcules” were later termed microbes, though he was one of the first to record them. -
Matthias Jakob Schleiden
By the early 19th century, even though the use of microscopes in botany seemed to fall out of practice, lawyer-turned-botanist Matthias Jakob Schleiden used them to study, and in 1838 make the observation that all plants are made of cells. -
Theodor Schwann
A year after Schleiden shared his plant cell theory, German biology professor Theodor Schwann hypothesized that it could also be applied to animals. Merging their ideas, Schleiden and Schwann worked together to develop what is now known as the cell theory, stating that cells make up all living organisms. -
Ignaz Philipp Semmelweiss
In the 1840s, while Schleiden, Schwann, and Siebold continued to develop their theories, Hungarian doctor Ignaz Philipp Semmelweiss was looking into the causes of his patient deaths to come to the conclusion that would be formalized about 10 years before his death,—that disinfecting hands and tools lowers the risk of infectious disease by getting rid of germs. -
Karl Theodor Ernst von Siebold
In 1845, building upon Schleiden and Schwann’s ideas, Siebold proposed that cells also made up microbes, which then made up plants and animals. This theory was later disproved, however, the idea that microbes were also living organisms and made up of the same material as plants and animals was correct. -
Rudolf Carl Virchow
In the 1850s, influenced by Schleiden and Schwann’s cell theory, Polish doctor Rudolf Carl Virchow had, with his many years of studying and treating patients, come to the conclusion that “all cells arise from cells,” by which logic he deduced that diseased cells grow from relatively healthy cells. This was proved to be somewhat true, and advanced research determining the difference between diseases of the cell and infectious diseases. -
Florence Nightingale
In the horrid conditions of the Crimean war, with soldiers ill and injured in unsanitary environments, English nurse Florence Nightingale led valiant efforts to clean and scrub every inch of the hospital. Recognizing the importance of cleanliness in the prevention and treatment of disease, she brought the death rate down by two-thirds. In 1860, she published her medical beliefs, promoting sanitation practices that strengthened hygiene standards in military hospitals. -
Louis Pasteur
In 1864, French chemist Louis Pasteur took to studying microbes and applied his findings to his work in fermenting wine and vinegar. He found that food and drink would spoil with the presence of certain microbes, which he later discovered could not survive in high heat. This was termed “pasteurization,” and led him to propose that microbes, which he called germs, could cause infections easily transmitted by humans. His theory became the foundation of the germ theory of disease. -
Joseph Lister
In 1867, Scottish surgeon Joseph Lister developed a use of chemicals to help reduce the spread of microbes to patients after surgery, bringing the death by infection rate down to 15%. -
Robert Koch
In 1876, German doctor Robert Koch experimented with healthy mice and diseased mice to find that specific microbes caused certain diseases. This discovery led him to find the causes of anthrax, tuberculosis, and cholera. Using the findings from his research, Koch developed the substance “agar,” to grow cultures of microbes that were uncontaminated.
