In 1959, MacGillavry met Escher. His work, the regular tiling of the plane, showed obvious links with the symmetry principles of crystallography. After seeking approval from the organisers (Joseph and Gabrielle Donnay), MacGillavry asked Escher to exhibit his lithographic works at the IUCr Congress in Cambridge, U.K. in 1960. The exhibition was a success, and as a consequence the IUCr commissioned MacGillavry to write the book under its auspices.