Abstract
The IUCr's close association with quantum crystallography, rightly celebrated by this focused anniversary issue, has its origins in regular meetings of experimentalists and theoreticians interested in electron charge and spin density back in the 1960s. That ad hoc group was adopted by the IUCr in the 1970s, when a Commission was created and latterly it has been renamed as the Commission on Quantum Crystallography. The history is summarized in this foreword to the issue.