"I never thought of myself as a great man, just a man who made a great discovery."

"I am not a hero. I just happened to be in the right place at the right time."

"My work was not a flash of genius, but a gradual unfolding of facts."

"The laboratory worker who is not prepared to meet with occasional failures will never achieve success."

"The mould was very interesting. I cultured it and found it produced a powerful antibacterial substance. It was very effective against staphylococci and other Gram-positive pathogenic bacteria."