Louis Pasteur (1822-1895) was a French chemist best known as the originator of germ theory and inventor of the process of Pasteurization. His many accomplishments include the development of numerous vaccines as well as the development of major breakthroughs that have revolutionized the way humans fights disease. His life's work also paved the way for pretty much all of microbiology and bacteriology. Despite several controversial blemishes on his legacy, Pasteur is viewed as one of the great scientific minds of the past 200 years.
"I am utterly convinced that Science and Peace will triumph over Ignorance and War, that nations will eventually unite not to destroy but to edify, and that the future will belong to those who have done the most for the sake of suffering humanity."
Source: Louis Pasteur, Free Lance of Science (1960) by René Jules Dubos, Ch. 3 "Pasteur in Action" (via Wikiquote)