John Maxwell Cowley. 18 February 1923 — 18 May 2004

Although John Cowley made important contributions across virtually the whole of crystallography, using electrons, X–rays and neutrons, his work in the three areas of short–range order, dynamical electron diffraction, and scanning transmission electron microscopy are of particular significance. In all of these areas his work involved theory and experiment in equal measure, with each reinforcing the other. The outcomes of these activities have now spread across so much of solid-state physics, metallurgy, structural inorganic chemistry and Earth sciences that they have entered the canon, with authors quite frequently no longer feeling the necessity of referring to specific papers on many of the matters of principle first enunciated by John.