Louis Ignarro
Ignarro is best known for his discoveries which concern the nitric oxide as a signaling molecule in the cardiovascular system. He won the Nobel Prize in Physiology or Medicine in 1998 for his discoveries. He shared the prize with Robert F. Furchgott and Ferid Murad. Due to nitric oxide indirectly being involved in the action of Viagra, he is sometimes referred to as the "Father of Viagra".