Group working on gaseous diffusion, c 1940s.
© Science Museum / Science & Society Picture Library
This picture shows the group of scientists pioneered the work of gaseous diffusion in the 1940s. The photograph was taken outside the Clarendon Laboratory at Oxford University in England. Gaseous diffusion was a method of separating uranium-235 from the more common uranium-238 by forcing a gas containing uranium through a series of barriers with very fine holes.