I went to London in November 2018 and visited the lab of Alexander Fleming where he discovered penicillin.
An author wrote this:

A poorly tidied up laboratory behind a miracle cure

In the summer of 1928, in a hurry to go on vacation, Scottish doctor Alexander Fleming left a pile of dirty Petri dishes in his laboratory sink. And as if that weren’t enough, the bottoms were smeared with staphylococci, the bacteria that cause boils, sore throats, and intestinal poisoning.

On his return a few weeks later, Dr. Fleming discovered an exciting thing in the mess of the sink: one of the Petri dishes was strewn with bacteria except where the mold had formed. There was nothing around as if an invisible barrier protected the area.

Taking a closer look at the phenomenon, he found that the mold, which belongs to a rare form of Penicillium Notatum, secreted a fluid that killed several chains of deadly bacteria. Alexander Fleming published his remarkable discovery — which has gone almost unnoticed.

Years later, Howard Walter Florey, an Australian pathologist, accidentally read Fleming’s article while leafing through old medical journals. Together with biochemist Ernst Boris Chain, they explored the therapeutic effects of the fluid secreted by mold. In 1941, they collected enough penicillin to administer it to the first human subject. This 43-year-old police officer contracted a fatal bacterial infection after being scratched by rose thorns in his garden.

The results were spectacular: the patient’s fever dropped, and his appetite returned. The penicillin used to treat him was quickly called a miracle drug. Unfortunately, due to a lack of supplies, the man’s infection flared up