Rosalind Franklin's main contribution to the understanding of DNA molecules was the production of high-resolution X-ray diffraction images of DNA fibers. These images, known as Photograph 51, provided crucial evidence for the helical structure of DNA. They showed that DNA had a regular, repeating structure and indicated the presence of a helix with specific dimensions and a repeating pattern of chemical groups. Franklin's images played a key role in the discovery of the double helix structure of DNA by James Watson and Francis Crick.
