Alexander Fleming on this day Sept 28 1928 discovered penicillin
In 1928, bacteriologist Alexander Fleming made a chance discovery from an already discarded, contaminated Petri dish. The mold that had contaminated the experiment turned out to contain a powerful antibiotic, penicillin. However, though Fleming was credited with the discovery, it was over a decade before someone else turned penicillin into the miracle drug for the 20th century.
How did this Petri dish almost get cleaned before being noticed? How did the mold get onto the dish? Who transformed penicillin into a useful drug?
http://history1900s.about.com/od/medicaladvancesissues/a/penicillin.htm