What if someone told you that washing your hands could save lives? In the 1800s, most people did not believe that. Hospitals were filthy places. Florence Nightingale, born May 12, 1820, set out to change that. Her wealthy family expected her to marry and host parties. Instead, she studied math and hygiene. When the Crimean War broke out in 1854, Britain sent soldiers to fight in what is now Ukraine. The army hospital at Scutari was overcrowded and full of disease. Nightingale arrived with 38 nurses. She demanded clean bedding, fresh air, and proper food. She kept detailed records of every death, tracking whether soldiers died from wounds or from infections they caught in the hospital. Her data showed that most deaths came from disease, not battle. This was a revolutionary idea. Army leaders resisted her changes. She went over their heads, writing directly to newspapers back in England. Public pressure forced the military to improve conditions. After the war, Nightingale used her fame to start the world's first professional nursing school in London in 1860. Her methods of collecting health data helped create the field of medical statistics.