Humankind doesn't advance without, well, humans. That's why medical advances are so critical to each and every one of us. Sir Alexander Fleming, along with Sir Ernst Boris Chain and Sir Howard Florey, made one of the most important medical discoveries ever and, as a result, won the 1945 Nobel Prize for Physiology or Medicine.
In his rather unclean research lab, and by accident, Fleming realized that a mold growing in a petri dish had killed adjacent Staphylococci bacteria. Thus began his experiments with the mold, called Penicillium notatum, which eventually resulted in penicillin-based antibiotics.
These drugs were effective against all sorts of diseases that had ravaged humans for centuries, including tuberculosis, gangrene, syphilis and many other bacterial infections. As a result, untold lives were improved or spared.