"I play with microbes. There are, of course, many rules to this play...but when you have acquired knowledge and experience it is very pleasant to break the rules and to be able to find something nobody…"

"I have been asked by many people how I came to discover penicillin. The answer is that I did not discover it. I just happened to notice it."

"The bacteriologist must be a patient man."

"The discovery of penicillin was a matter of chance, but the application of it was a matter of hard work."

"It is a wonderful thing to be able to save lives with a simple substance."