The past decade has witnessed escalating interest in solidstate phase transitions that involve significant changes in structure without appreciable loss of crystal mosaicity— single crystal to single crystal (SC-SC) transformation.[1–5] Several factors have contributed to these studies: increased general access to X-ray diffraction facilities, softwareassisted demystification of crystallography, technological developments leading to rapid intensity data collection, and the popularization of crystal engineering as a research field. The two most active areas of interest with regard to SC-SC transformations are the development of porous materials and solventless topochemical reactions. Recent new results representing the current state-of-the-art with regard to both of these topics are reported in the Research Front of this issue of the Australian Journal of Chemistry. In 1988 Dunitz, Schomaker, and Trueblood recounted a prior statement by Nobel Laureate (chemistry, 1939) Leopold Ruzicka, that ‘a crystal is a chemical cemetery’. This was interpreted to imply that, in sharp contrast to liquids and gases, the solid state consists of molecules that are lifelessly interred in fixed geometrical arrangements with little prospect of an interesting existence.[6] However, it has long been known that structural rearrangement can occur in the solid state in response to a variety of physical or chemical factors. Provided that these structural changes are subtle, it is reasonable to expect that the relative absence of mechanical stress would allow individual crystals to retain their mosaicity, both during and after transformation. In most cases, though, changes of the chemical composition and/or molecular conformation and/or packing arrangement within crystals are well known to cause catastrophic disruption of packing continuity. Concomitant fracturing of