The inclusion of small guest molecules into porous crystalline materials promises several exciting innovations in a wide range of areas, including separation and storage of gases or vapors, chemical sensing, and catalysis. Using now well-established principles of crystal engineering we can aspire to design porous materials with tailored structural and physical properties. However, there is still much need to develop new approaches to understanding the sometimes-complicated relationships between molecular-level structure and physico-chemical properties. In this regard, devising a range of complementary experiments to characI{Sterize materials under controlled environments such as gas pressure can be particularly challenging. This presentation will describe the development and application of a suite of new approaches to structural analysis by means of in situ X-ray diffraction,¹ complemented by physico-chemical characterization using a combination of gas sorption analysis and a unique system for pressure-gradient differential scanning calorimetry.^2,3 A number of examples from the recent literature will be presented.