This lesson is about John Snow, an English physician and pioneer in anesthesia and epidemiology. Snow’s groundbreaking work led to the widespread adoption of anesthesia as well as a significant improvement in public health around the world. Snow was the first to demonstrate the link between contaminated water and the spread of cholera. As a result, he advocated for clean drinking water and sewers. Eventually, these innovations were adopted around the world, “thus likely saving millions of lives.”