The famous X-ray crystallography image of DNA from calf thymus, taken by Rosalind Franklin and Ray Gosling. Linus Pauling's annotations are to the right of the photo. May 2, 1952. It says: “Franklin& Gosling. Sodium deoxyribose nucleate Type B”.
Jim Watson wrote: “The instant I saw the picture my mouth fell open and my pulse began to race. The pattern was unbelievably simpler than those obtained previously (“A” form). Moreover, the black cross of reflections which dominated the picture could arise only form a helical structure.” From The Annotated and Illustrated Double Helix, edited by Alex Gann and Jan Witkowski.
Suggested by Jeff Karr, ASM Archivist