Photo 51 is the nickname given to an X-ray diffraction image of DNA taken by Raymond Gosling in May 1952 in the lab of Rosalind Franklin where he was her PhD student at King’s College London in Sir John Randall’s group. It was critical evidence in identifying the structure of DNA.
A tiny sample of hydrated DNA was mounted inside and then an X-ray beam shone at it for more than 60 hours. The beam of X-rays scatter and produce an image from which a 3D structure can be determined.
The resulting striped cross shape you can see may not mean much to the casual observer, but to a small group of scientists it proved to be a revelation.
It was shown by Maurice Wilkins of King’s College to James Watson at the Cavendish Laboratory in Cambridge, who said “my mouth fell open and my pulse began to race”.