On February 14th 1929, Alexander Fleming introduced his discovery of Penicillin to the world.
Working at St. Mary’s Hospital in London the Scottish bacteriologist found that cultures of Staphylococcus Aureus (a common bacterium found in humans) had been contaminated with a mould and the Staphylococcus growth around the mould had been dissolved. On closer inspection of the mould Fleming identified the mould as penicillium notatum as found on bread.
Fleming introduced his findings of a cheap and easy to reproduce antibiotic to the world and this discovery has saved countless lives. Antibiotics are natural chemicals released by bacteria and moulds to inhibit growth of other organisms.