Alexander Fleming was a Scottish bacteriologist who had been conducting research on staphylococci, a type of bacteria responsible for various infections. On a return to his laboratory after a vacation, he observed something unusual: one of his petri dishes, which had been accidentally contaminated with mold, was displaying an unexpected reaction. The mold, which he later identified as Penicillium notatum, not only thrived but demonstrated the ability to inhibit the growth of staphylococci. This accidental discovery led Fleming to investigate the properties of the mold further.

Fleming's deepening research revealed that the mold produced a substance that was effective against a variety of harmful bacteria. He dubbed this substance penicillin, and his findings were published in 1929, although it would take years for penicillin to be developed into a usable treatment. Fleming's work initially did not garner immediate attention in the scientific community. However, it laid the foundation for the development of antibiotics, which would not be fully realized until researchers Howard Florey and Ernst Boris Chain advanced penicillin production techniques in the late 1930s and 1940s.

The mass production of penicillin during World War II made it accessible for treating soldiers and civilians afflicted with infections, saving countless lives. This event marked the beginning of the antibiotic era, fundamentally transforming medical treatment protocols and leading to further discoveries in the field of bacteriology and pharmaceuticals.