The past decade has witnessed escalating interest in solid-state phase transitions that involve significant changes in structure without appreciable loss of crystal mosaicity–single crystal to single crystal (SC-SC) transformation. 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 this Research Front.