ArgumentThe discovery of electron diffraction by George Paget Thomson in Aberdeen and Clinton J. Davisson and Lester H. Germer at the Bell Labs has often been portrayed as an example of independent discovery. Neither team was particularly interested in the developments of the nascent quantum theory but they both ended up demonstrating one of the most striking experimental consequences of the new physics. This paper traces the aftermath of this discovery and the way electron diffraction immediately turned from empirical evidence (...) of a highly novel theory into a technique for applied and technological research. Thomson was the first to design an “electron diffraction camera,” an instrument that soon found its place in laboratories around the world. I discuss the role played by Davisson and Germer, and by Thomson in the development of electron diffraction as a “research technology,” taking into account their specific institutional settings and research cultures. While Davisson and Germer remained in the industry-oriented Bell Labs, Thomson moved to Imperial College in 1930 where collaboration first, and competition later with George I. Finch was also relevant for the consolidation of an instrument that eventually became widely known as the “Finch Camera.”. (shrink)