Scientist Robert F. Furchgott died at the age of 92 on May 19 in Seattle. His Nobel Prize-winning research led to the development of the erectile dysfunction drug Viagra.

Furchgott and two other American scientists were awarded the 1998 Nobel Prize for Physiology or Medicine for discovering that nitric oxide transmits signals within the human body. This research led to many breakthroughs, including new treatment for pulmonary hypertension in newborns, and of course, Viagra.

Mr. Furchgott is survived by three daughters, four grandchildren and one great-grandchild.