While competing in a game show called 'The greatest science investigator of all time', famous scientists from history describe their life's work and explain why they deserve the title. On this show it's the turn of Sir Alexander Fleming, who describes how in 1928 he discovered penicillin, which kills some bacteria responsible for serious human infections. The most important part of the discovery happened while he was away on holiday. A blob of mould had grown on a dirty dish in his lab. All around the mouldy blob, there were no bacteria growing. He reasoned that something in the mould was killing the bacteria. This substance is what he later called penicillin. This discovery led to a group of medicines called antibiotics, which have saved countless lives.

First broadcast:
5 March 2008

Useful as an introduction to Sir Alexander Fleming and his discovery of penicillin. The names displayed at the start of the clip could be used for children to research a specific person's scientific discovery and its effect on current science. They could make a biography about Sir Alexander or other scientists. For the other scientists in the clip, the children could use their research to create a similar clip pretending to be that scientist and explaining why they are the greatest scientist!