"It is not enough to discover a thing; one must also know how to use it."

"It is a happy accident that the mold grew on my plate, but it was not an accident that I recognized it."

"I had no idea that I would be involved in such a great discovery. It was purely accidental."

"I did not invent penicillin. Nature did. I just found it."

"The thought that I might have discovered something which would be of value in treating disease was, of course, uppermost in my mind."