Seeing the Unseen Causes of Disease: Nine Scientists From Early Microscopes to mRNA Vaccines

Dutch spectacle maker traditionally credited, with Hans Lippershey, with building an early compound microscope around 1590. The claim rests on testimony his son Johannes gave in 1655, and several historians concluded the story was invented, so the path opens with an origin the evidence does not settle.

From the 1670s this self-taught tradesman ground his own single lenses, which magnified far beyond the compound microscopes of his day. He was the first person to observe and describe bacteria, protozoa, spermatozoa and red blood cells, and he reported what he saw in roughly 560 letters.

Koch moved from seeing microbes to proving what they do. He worked out the life cycle of the anthrax bacillus in 1876, identified the tuberculosis bacillus in 1882, and set out criteria, Koch's postulates, for showing that a specific microorganism causes a specific disease. He won the 1905 Nobel Prize in Physiology or Medicine.

Studying tobacco mosaic disease in 1892, this Russian botanist found that sap from infected plants stayed infectious after passing through a Chamberland filter fine enough to remove every known bacterium. He read the result as a bacterial toxin, so its full meaning was missed in his lifetime.

Repeating the tobacco mosaic filtration experiment independently in 1898, Beijerinck concluded the filterable agent was a new kind of self-replicating infectious matter, not a toxin, and named it a virus. He also saw that it could reproduce only inside a living host.

In 1910 at the Rockefeller Institute, Rous showed that a tumor in a hen could be passed to other chickens with a cell-free, filtered extract, evidence that a virus could cause cancer. Cancer was assumed to arise wholly inside the cell, and the discovery waited 56 years for the 1966 Nobel Prize in Physiology or Medicine.

In 1935 Stanley purified tobacco mosaic virus into crystals, showing a virus behaving as a definable chemical substance. His later work found the crystals were made of protein and ribonucleic acid. The work shared the 1946 Nobel Prize in Chemistry and helped found the molecular study of viruses.

A Hungarian and American biochemist who specializes in RNA-mediated mechanisms, particularly in vitro-transcribed messenger RNA for protein replacement therapy. She laid the scientific groundwork for mRNA vaccines despite skepticism in the scientific community, and shared the 2023 Nobel Prize in Physiology or Medicine.

An American physician and immunologist known for his contributions to RNA biology, now director of the Penn Institute for RNA Innovation at the University of Pennsylvania. With Katalin Kariko he received the 2023 Nobel Prize in Physiology or Medicine.