Cryogenic electron microscopy enables structural and spectroscopic characterization of beam-sensitive materials that are otherwise unstable under conventional imaging conditions. Many functional interfaces in energy and environmental systems, such as solid–electrolyte interphases in lithium batteries, ionomer films in fuel cells, and pigment–binder matrices in cultural heritage materials, are chemically reactive, physically volatile, or highly susceptible to radiolysis and contamination. Cryogenic workflows preserve these systems in vitrified or low-temperature states, allowing transmission electron microscopy (TEM), scanning TEM (STEM), and electron energy-loss spectroscopy (EELS) to operate within safe dose limits while maintaining access to nanoscale structural and chemical detail. This thesis applies cryo-TEM, cryo-STEM, cryo-EELS, and cryo-focused ion beam (cryo-FIB) milling to enable nanoscale characterization across a range of beam-sensitive energy materials. A dimensionality reduction framework is developed to extract chemically meaningful information from low-signal STEM-EELS datasets, allowing multilayered interphases at lithium-metal interfaces to be spatially resolved. In alkaline fuel-cell catalyst layers, cryogenic imaging distinguishes ionomer from carbon support and identifies contamination artifacts that arise at room-temperature. Film thickness and coverage are quantified as functions of deposition method and solvent formulation. In historical CdS-based pigments, cryo-STEM imaging reveals stacking disorder in individual nanocrystals, and density functional theory (DFT) modeling shows how such disorder modulates exciton behavior and promotes degradation under illumination. Across all three systems, cryogenic electron microscopy extends the analytical reach of electron imaging and spectroscopy into materials that would otherwise degrade, transform, or contaminate during preparation and acquisition. The techniques demonstrated here enable direct measurement of chemical bonding, structural order, and interface morphology in complex, radiation-sensitive systems. Together, these studies establish cryo-EM as a versatile platform for nanoscale characterization of reactive soft matter, with implications for electrochemical performance, materials stability, and long-term degradation across both modern energy devices and historical materials.