DNA
Erwin Chargaff was an Austro-Hungarian-born American biochemist who is best known for his discovery of DNA “base ratios,” also known as “Chargaff’s rules,” in the late 1940s, while working at Columbia University in New York City.This Chargaff's rules state that DNA from any cell of all organisms should have a 1:1 ratio (base Pair Rule) of pyrimidine and purine bases and, more specifically, that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine.This thing were later to later pave the way for  James Watson and Francis Crick to the double helical structure of the DNA.