
In 1952, Rosalind Franklin and Raymond Gosling exposed a hydrated DNA fibre to X-rays for 62 hours, producing Photo 51: the pattern that helped Watson and Crick build the correct double-helix model months later
In May 1952, Rosalind Franklin and Raymond Gosling exposed a single hydrated DNA fibre to an X-ray beam for 62 hours in a basement at King's College London. The resulting Photo 51 showed the helix so clearly that its geometry could be read straight off the plate — months before Watson and Crick built their model.











