Alexander Fleming was a scientist who was working on staphylococci. These are the germs that make wounds go septic. Whilst cleaning the culture dishes one day he saw a mould growing on one of the plates. This in itself was not unusual, but on this occasion there were no germs growing around the growth. Curious as to what caused the germs to stop growing, and eager to find out what the mould was, Fleming grew more of it and experimented. He found that the mould acted against anthrax and diphtheria without creating any harmful side effects. This was the first occasion that an antibiotic drug had been developed (an antibiotic is something naturally produced by living organisms, rather than being a chemical compound). The new drug was a member of the penicillin notatum family, known popularly as penicillin.
Fleming however did little with his discovery. It wasn’t until 1935 when researchers Florey and Chain at Oxford University saw Fleming’s research papers that the drug was developed further.