slated to appear in the December 2025 issue of Structural Chemistry (Vol 36, Issue No 6) The world of structural chemistry mourns the passing of Alan L. Mackay on February 24, 2025. Our journal Structural Chemistry (Springer Nature) will publish a special collection of contributions honoring him – the contributions to this collection may be most broad-based, including any aspects of crystallography, other domains of structural chemistry in concert with Mackay’s views of generalized crystallography.