The term cell was coined by Robert Hooke. One of the illustrations in his work Micrographia from 1665 shows a thin slice of cork. It seems to consist of smaller units encased by walls. They reminded Hooke of the cells inhabited by monks and nuns. This later became a fundamental concept in physiology. But the physiological importance of cells was unknown to Hooke. 

Antonie van Leeuwenhoek was the first to document living cells. In 1674, he was able to observe the red blood cells of a fish. Leeuwenhoek was a Dutch draper and shop owner in Delft and made magnifying lenses of superior quality to scrutinise fabric quality. From 1670, he directed his lenses on the world around him and discovered what no one had seen before. This includes living bacteria, which he first noted in 1683. Like Hooke, he did not know what he was seeing. 

In 1838, the botanist Jakob Schleiden published the theory that cells are structural units shared by all plants. The same year, he and the physiologist Theodor Schwann defined their cellular theory: all forms of life consist of cells, the fundamental structural unit of all organisms. 

Oscar Hertwig was a German anatomist and embryologist with a keen interest in cells and cell cores. His research on fertilisation, reproduction and heredity has been vital to our knowledge in these fields. In 1876, he was the first to describe meiosis, the type of cell division that produces sperms or egg cells. Later, he also described the role of nuclein (nucleic acid) in the fertilisation and transmission of hereditary characteristics.   

Otto Warburg was awarded the Nobel Prize for his biochemical research into how energy is released in the chemical processes of living cells.

Hans Krebs was awarded the Nobel Prize for his medical discovery of the citric acid cycle, the central cellular metabolic process that breaks down nutrients and releases chemical energy in the form of ATP (adenosine triphosphate).

Peter Mitchell explained how ATP molecules transfer energy in cells. This discovery helped to explain fundamental processes such as cell respiration, photosynthesis and bacterial metabolism. 

Hugo Theorell showed how oxidative enzymes affect cell respiration. His research laid the foundation for the modern understanding of how cells produce energy from oxygen and nutrients. 

In 1940, Ulf von Euler found that noradrenaline is a signal substance in the nervous system, and was awarded the medicine prize in 1970 for his discovery.  

The Nobel Prize in Physiology or Medicine 1982 was awarded jointly to Sune K. Bergström, Bengt I. Samuelsson and John R. Vane "for their discoveries concerning prostaglandins and related biologically active substances." Prostaglandins have been vital to the development of medications in a variety of fields, such as the treatment of blood clots, inflammations and allergies. 

William Kaelin, Peter Ratcliffe and Gregg Semenza were awarded the medicine prize in 2019 for their work on how cells can detect and adapt to the oxygen supply.

In 1664, Thomas Willis presented what was until then the most complete and correct description in text and images of the human nervous system. In his work Cerebri anatome, he drew up an informed overview of the central and autonomous nervous systems’ anatomy. He also distinctly classified the cranial nerves, including the “Willis nerve”, identified the sympathetic system and defined the brain as the organ of thinking. This was the context in which the word “neuro” was first used in medicine, but it did not get its current meaning until the 19th century. 

Gustaf Retzius made meticulous microscopic studies of the structure of the brain and nervous system. He was highly skilled in preparing and dying the fragile nerve cells, and also a fantastic draughtsman, working with the very best printers. Retzius was a professor of histology at KI in 1878–1890. He also studied skeletons and skulls to determine their age, gender and any diseases. He believed he could see from the bones what nationality and “race” they were. 

The Nobel Prize in Physiology or Medicine 1906 was awarded jointly to Camillo Golgi and Santiago Ramón y Cajal “in recognition of their work on the structure of the nervous system.”

Charles Sherrington studied reflexes by charting the links between muscular movements and electric impulses to the nerves. Edgar Adrian succeeded in measuring electric impulses in an individual nerve. They were jointly awarded the Nobel Prize in Physiology or Medicine 1932.

John Eccles, Alan Hodgkin and Andrew Huxley delved deeper into the nervous system to study how electric signals are transmitted. They were awarded the medicine prize in 1963.

Ragnar Granit, Haldan Keffer Hartline and George Wald made ground-breaking discoveries about vision and the physiology of the eye. They were awarded the Nobel Prize in Physiology or Medicine 1967.

The Nobel Prize in Physiology or Medicine 1981 was divided, one half awarded to Roger W. Sperry “for his discoveries concerning the functional specialization of the cerebral hemispheres,” the other half jointly to David H. Hubel and Torsten N. Wiesel “for their discoveries concerning information processing in the visual system.”

Arvid Carlsson, Paul Greengard and Eric R. Kandel, awarded the medicine prize in 2000, examined how signals are chemically transmitted by various substances between synapses, the contact points between cells in the nervous system. 

The Nobel Prize in Physiology or Medicine 2014 was divided, one half awarded to John O'Keefe, the other half jointly to May-Britt Moser and Edvard I. Moser “for their discoveries of cells that constitute a positioning system in the brain.”

To study how traits are inherited, the biologist and Augustinian friar Gregor Mendel cross-fertilised pea plants with different traits, such as green or yellow peas, and studied several generations of offspring. He concluded that traits were passed on in pairs, one from each parent. The characteristics of their offspring is determined by whether these traits are dominant or recessive. 

In 1878, the biologist Walther Flemming dyed cells from newt larvae and could then detect blue formations, chromosomes, inside the cells under a microscope. He could also observe processes in the cell core, including the behaviour of chromosomes in both living and dead cells. Flemming was the first to describe in detail how chromosomes behaved during normal cell division. It was he who came up with a name for the process: mitosis. 

Wilhelm von Waldeyer, a professor of anatomy in Berlin, coined the term “chromosome” in 1889, to describe the already-observed parts of the cell that particularly absorbed pigments when dyed. He was one of the earliest and most enthusiastic advocates of Cajal’s “neuron theory” on the structure of the nervous system.   

At the end of the 19th century, the Uppsala professor Olof Hammarsten studied ‘nucleic acid’ (DNA and RNA), a fundamental constituent of the cell. The preparation methods of the time smashed the DNA molecules to smithereens when they were examined. Scientists did not realise how big the molecule was, and didn’t believe it could carry the genetic information. In the 1930s, Olof Hammarsten’s nephew Einar Hammarsten, a professor of chemistry at KI, succeeded in proving that DNA is a “macro molecule.” Under the microscope, he managed to unwind fibres that were up to 50 cm long. 

The geneticist Vilhelm Johannsen in Copenhagen was of the generation of scientists who collectively, but independently of each other, rediscovered Gregor Mendel’s research on heredity from the 1860s. Mendel’s genetics were widely launched from around 1900. Mendel formulated the first modern genetic theories, and his observations on dominant and recessive genes are still valid. 

Thomas Hunt Morgan studied fruit flies with genetic changes, mutations, such as an extra leg, no antennae, or different wing shapes. He examined how these traits were inherited, and how they are linked to chromosomes. He was awarded the Nobel Prize in Physiology or Medicine 1933.

In 1936, Torbjörn Caspersson embarked on a lifelong research project at KI into nucleic acid with biophysical methods, and particularly optical ones. He managed in the first year to measure the level of DNA and RNA in individual cells using a new technique for ultraviolet microscopy. In this way, he could prove that nucleic acid was involved in reproduction, since the content varied at different stages of cell division.  
Caspersson became a professor of cellular research and genetics at the KI in 1944, and was later appointed head of a department at the Medical Nobel Institute. 

Oswald Avery showed in 1944 that DNA contains the cell’s genetic information. Until then, the dominating assumption was that something as complicated as genes must be packaged in a correspondingly complex macro molecule, most likely a protein. DNA has a comparatively simple chemical structure and was therefore discounted. Although Avery could demonstrate that genetic information was contained by DNA, it was still unclear how the molecule coded the information. 

A ground-breaking step in genetic research was made in 1953, when Francis Crick and James Watson managed to determine the structure of the DNA molecule. This discovery was enabled by research by Rosalind Franklin, who died in 1958. The 1962 medicine prize was awarded to Crick, Watson, and Maurice Wilkins, a colleague of Rosalind Franklin. 

The CRISPR-Cas9 method, also known as “gene scissors”, makes it possible to modify genetic contents. Emmanuelle Charpentier and Jennifer Doudna were awarded the medicine prize in 2020.