On returning to the lab from summer holiday, Alexander Fleming noticed that one his bacteria cultures was contaminated with mould. The colonies of staphylococci immediately surrounding the mould had been destroyed, whereas other staphylococci colonies farther away were normal. However, it would not be fair to limit Fleming’s work to a fortunate stroke of serendipity; rather, it was a chance reward for tenacity. As a bacteriologist, he had spent decades looking for antibacterial substances to overcome the problems of the available antiseptics. This is the history of the first widely available antibiotic, which was developed after numerous scientific breakthroughs by many other scientists. Since the serendipitous discovery of its active ingredient (penicillin) until mass production of a viable drug was eventually achieved.