Book excerpt: Deep subsurface characterization technologies and demands are changing rapidly within the energy industry. In this swiftly evolving landscape, the wide range of analyses performed on the rocks and fluids obtained from cores remain fundamental tools in managing subsurface uncertainty and associated risk. During the energy transition large volumes of newly acquired and legacy core will be accessed to better understand both existing hydrocarbon resources and other subsurface energy-related systems, particularly for carbon capture, utilization and storage (CCUS), geothermal energy and the long-term storage of nuclear waste. Through state-of-the-art reviews and case studies this volume illustrates how innovative approaches continue to create value from both new and historical cores recovered for deep subsurface reservoir characterization and storage complex evaluation. Such an assessment is timely given that the sector sits at a pivotal point in terms of changing technologies, economics, demographics, skillsets and energy solutions.