In 1934, J.D. Bernal and Dorothy Crowfoot Hodgkins of Birkbeck College at the University of London, demonstrated that aqueous crystals of the protein pepsin could diffract X'rays.
"The wet crystals gave individual X-ray reflections, which were rather blurred owing to the large size of the crystal unit cell, but which extended all over the films to spacings of about 2 Å. That night [in late April, 1934], Bernal, full of excitement, wandered around the streets of Cambridge, thinking of the future and how much it might be possible to know about the structure of proteins if the photographs he had just taken could be interpreted in every detail." (Hodgkins & Riley, 1968)
