Sir Alexander Fleming  (6 August 1881 – 11 March 1955)

Sir Alexander Fleming was a young bacteriologist when an
accidental discovery led to one of the great developments
of modern medicine on September 3, 1928. Having left a
plate of staphylococcus bacteria uncovered, Fleming noticed
that a mold that had fallen on the culture had killed many of
the bacteria. He identified the mold as penicillium notatum,
similar to the kind found on bread.

In 1929, Fleming introduced his mold by-product called
penicillin to cure bacterial infections.