Erwin Chargaff was an Austro-Hungarian-born American biochemist, writer, and professor of biochemistry at Columbia University medical school. A Bucovinian Jew who immigrated to the United States during the Nazi regime, he penned a well-reviewed autobiography, Heraclitean Fire: Sketches from a Life Before Nature. Through careful experimentation, Chargaff discovered two rules, called Chargaff's rules, which helped lead to the discovery of the double helix structure of DNA.