Then
His publication was initially overlooked, but Florey and Chain’s team later extracted working penicillin, saving enormous numbers of lives in World War II.
Timeline of Discovery · 26 / 30
Alexander Fleming
1881 - 1955 · Scotland
Alexander Fleming noticed that a stray mould killed bacteria — a single observation that led, through later work, to the first antibiotic, penicillin.
- Medicine
- Biology
- Industrial & Modern
Lived
1881 - 1955
Era
Industrial & Modern
Primary field
Medicine
Signature idea
Discovered penicillin, revolutionising medicine
Their place in history
1881 - 1955
The question they asked
What killed the bacteria in my dish, and can a natural substance fight bacterial infection?
The Contribution
What this scientist actually did — precisely and plainly.
He observed that a mould (Penicillium) destroyed surrounding bacteria, named the substance penicillin, and his discovery was later purified and mass-produced as the antibiotic era’s first drug.
How the Work Advanced Knowledge
The tools, experiments and reasoning behind the discovery.
He was a meticulous observer who noticed an anomaly others might discard, then tested the mould’s effect on stubborn bacteria.
Why It Mattered Then / Today
From their own moment in history to the world we live in now.
Today
Antibiotics remain a cornerstone of medicine — and their overuse is why antimicrobial resistance is now one of the world’s great health challenges.
Important Works or Discoveries
Landmarks that carried the idea into the world.
- Discovery of penicillin
- Nobel Prize in Physiology or Medicine 1945 (shared)
- Lysozyme research
One sometimes finds what one is not looking for.
Sources
Where this profile was verified.
Last reviewed: 2026-09-22
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