In 1913, George Papanicolaou arrived at Ellis Island from Greece; little did he know that within a decade he would accidentally discover one of the most effective cancer-screening tests in history. It took the medical community 20 years to adopt the simple Papanicolaou-or “Pap”-test, but once it did, the death rate associated with cervical cancer in the United States dropped more than 70 percent.

After studying medicine and zoology in Greece, Germany, and France, Papanicolaou served in the Greek Army during the Balkan War. The scientist learned about research opportunities in America from United States volunteers and decided to immigrate. During his first year in the States, he worked as a clerk for a Greek-language newspaper and played the violin at restaurants, but he was soon offered a position as a research biologist at Cornell University Medical College.

In 1916, Papanicolaou and his colleague Charles Stockard used guinea pigs’ eggs to study the role of chromosomes in sex determination. In order to ascertain when the eggs were ready to be removed, Papanicolaou examined the changes in the guinea pigs’ vaginal discharges by studying “smears” under a microscope. By 1923, the researcher had shifted his attention from guinea pigs to humans.

One day, while studying a sample taken from a purportedly healthy volunteer, Papanicolaou observed some abnormal cells. His interest piqued, he obtained smears from women known to have cervical cancer. The same type of cells turned up on his slides again. Papanicolaou had stumbled across a simple, relatively noninvasive way to detect cancer. Unfortunately, other doctors felt that traditional invasive biopsies were much more reliable than Papanicolaou’s surface swab.

Papanicolaou persevered and found an ally in Cornell gynecologist Herbert Traut. In 1939, the pair convinced the New York Hospital to use Papanicolaou’s test on all female patients. When Traut  and Papanicolaou published their findings in 1943, the scientific community could no longer deny that the test was effective. The test could be easily incorporated into exams and could detect abnormal cells in their precancerous phase. In 1960, the American Cancer Society campaigned for the widespread adoption of the Pap test. Papanicolaou died two years later at age 79, after 47 years at Cornell. Today, his test is a routine part of yearly gynecological exams and has saved the lives of hundreds of thousands of women.