They looked and saw Rosalind Franklin's X-ray crystallography which sparked them to think about the double-helix structure, and from there, they played around with cafeteria items (forks and spoons and whatnot) to create a model that finally worked.
How did Watson and Crick describe the structure of DNA?
Watson and Crick showed that each strand of the DNA molecule was a template for the other. During cell division the two strands separate and on each strand a new "other half" is built, just like the one before. ... By 1962, when Watson, Crick, and Wilkins won the Nobel Prize for physiology/medicine, Franklin had died. ;
Watson and Crick's DNA model, proposed in 1953, was greatly influenced by the research of Rosalind Franklin, Maurice Wilkins, and Erwin Chargaff. Franklin's X-ray diffraction data illustrated the helical structure of DNA, while Chargaff's rules explained base pairing. Their collaboration emphasized how scientific discoveries are often built on the work of others.
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