What were some major medical discoveries in the

16th century

* Andreas Vesalius publishes De humani corporis fabrica, the first accurate and detailed atlas of human anatomy.

* Paracelsus introduces the concept of iatrochemistry, the use of chemicals to treat diseases.

* Ambroise Paré develops new surgical techniques, including the use of ligatures to stop bleeding.

17th century

* William Harvey discovers the circulation of blood.

* Antonie van Leeuwenhoek invents the microscope, allowing scientists to see microorganisms for the first time.

* Edward Jenner develops the smallpox vaccine, the first successful vaccine.

18th century

* Joseph Lister introduces antiseptic surgery, which greatly reduces the risk of infection.

* James Lind discovers that citrus fruits can prevent scurvy.

* Edward Jenner develops the smallpox vaccine, the first successful vaccine.

19th century

* Louis Pasteur discovers that microorganisms cause disease and develops the process of pasteurization.

* Robert Koch develops the germ theory of disease, which states that specific microorganisms cause specific diseases.

* Joseph Lister introduces antiseptic surgery, which greatly reduces the risk of infection.

* Wilhelm Röntgen discovers X-rays, which allow doctors to see inside the body without surgery.

* Alexander Fleming discovers penicillin, the first antibiotic.

20th century

* Jonas Salk develops the polio vaccine.

* Francis Crick and James Watson discover the structure of DNA.

* Rosalind Franklin and Maurice Wilkins discover the structure of DNA.

* Christiaan Eijkman discovers that beriberi is caused by a deficiency of thiamine.

* David Bruce discovers that African sleeping sickness is caused by a protozoan.

* Ronald Ross discovers that malaria is transmitted by mosquitoes.

* Paul Ehrlich develops the first synthetic drug, salvarsan, to treat syphilis.

* Gerhard Domagk discovers the antibacterial properties of sulfanilamide.

* Alexander Fleming discovers penicillin, the first antibiotic.

* Selman Waksman discovers streptomycin, the first antibiotic effective against tuberculosis.

* Jonas Salk develops the polio vaccine.

* Maurice Hilleman develops the measles, mumps, and rubella (MMR) vaccine.

* Albert Sabin develops the oral polio vaccine.

* James D. Watson and Francis Crick discover the structure of DNA.

* Kary Mullis develops the polymerase chain reaction (PCR), a technique for amplifying DNA.

* Robert Edwards and Patrick Steptoe perform the first successful in vitro fertilization (IVF) procedure.

* Craig Mello and Andrew Fire discover RNA interference (RNAi), a process that controls gene expression.

21st century

* The Human Genome Project is completed, providing a complete sequence of the human genome.

* CRISPR-Cas9 gene editing technology is developed, allowing scientists to precisely edit DNA.

* The first artificial organ, a windpipe, is transplanted into a human patient.

* The first 3D-printed organ, a liver, is transplanted into a rat.