In 1950 Maurice Wilkins was working at King's College, London and using X-ray diffraction to create well-defined images of DNA. The images were of exceptional clarity. And it was this research and the images that were created in the Wilkins lab that sparked James Watson's interest in DNA. The young scientist became convinced that they could help unravel the mystery of the blueprint of life.
In 1951 Wilkins informed Crick and Watson that his studies indicated a double helical structure for DNA. Using this knowledge they constructed their first DNA model, but it had the phosphate backbones in the center. Rosalind Franklin, who was working with Wilkins, informed them that they were wrong because the backbones are hydrophilic and should be on the outside of the structure where they can interact with water.
In 1952, Franklin and colleague Raymond Gosling produced the now famous Photo 51 X-ray diffraction image of DNA. Wilkins showed it to Crick and Watson the following year. "The instant I saw the picture my mouth fell open, and my pulse began to race," remembered Watson in the book The Double Helix (1968). After seeing the image Crick and Watson redoubled their model making efforts and the eureka moment came on February 28, 1953. The Nature paper was published in April 1953 which proposes the double-stranded base pairing model that we now recognize; that is where the phosphate backbone is on the outside, and the paired bases point inward, like the rungs of a ladder.
In that same edition of Nature, Wilkins, Franklin, and Gosling published articles about their X-ray diffraction studies which supported the Crick and Watson model.