1854, cholera broke out in London, and more than 500 people died in 10 days. According to the prevailing view at that time, cholera was spread by air. But Dr. john snow doesn't believe this statement. He thinks cholera is spread by water. Si Nuo studied the relationship between the distribution of local wells and the distribution of cholera patients through punctuation map, and found that the incidence of cholera was obviously high within the water supply range of a well in Broad Street (or translated as Braud Street), and finally found the cause of cholera outbreak through this clue: a polluted pump. Shortly after people removed the handle of the pump, the incidence of cholera dropped significantly. John snow's work in this incident is regarded as the beginning of epidemiology.

During the period of 1948-1952, Richard Dole and Bradford Hill cooperated in a case-control study. By investigating the smoking history of cancer patients, they announced that there was a causal link between smoking and lung cancer. After more than 20 years, their cohort study further strengthened this conclusion. Their achievements provide a scientific basis for tobacco control actions.