Sharon Gabay · CC BY-SA 3.0

Working at the Technion in Haifa, Aaron Ciechanover helped identify ubiquitin, the small protein cells attach as a tag to mark other proteins for destruction, solving the long-standing puzzle of how cells break down and recycle their own material on schedule. He shared the 2004 Nobel Prize in Chemistry for the discovery with Avram Hershko and Irwin Rose; the mechanism turned out to matter for understanding cancer and neurological disease.