It all started in 1982, in a hospital in Western Australia. Young resident Dr. Barry Marshall was pondering the problems of ulcers and their intractability. The story is wonderful. Read the whole story right here. It might seem that the medical community was being obtuse in not recognizing what Dr. Marshall had found. Dr. Marshall's lack of status as a researcher (he was a practicing internist) and brashness didn't help. But - this is the way science works. New ideas are not accepted widely until the evidence for them builds up sufficiently that it convinces everyone. This is what Dr. Marshall did - in spite of the rejections he kept right treating and curing ulcer patients until he could not be ignored any longer.
Note the incident where he made an important connection because of an ulcer patient who also had a gum infection. Marshall realized that maybe an antibiotic was the key to ulcers. This is where science gets creative - the brain puts together two things that might seem unrelated and comes up with a new and important insight. To quote Louis Pasteur, "Chance favors the prepared mind."
The 2005 Nobel Prize in Physiology or Medicine