It is International Nurses Day which is celebrated on the birthday of Florence Nightingale.
She was a fantastic nurse but also a brilliant mathematician. Her use of statistics saved thousands of lives and changed medicine for everyone around the world.
Have a look at these websites for more information:
This is a copy of a chart she created (pictured above). She used statistics to show that more soldiers died from disease than from battle wounds. This helped convince people to change their ways and improve medicine.
Watch the video from BBC True Stories