This chapter describes in detail the characterization techniques and the properties of ionic liquids, nanofluids, and nanomaterials. It takes into consideration ionic liquids’ physicochemical properties, including low vapor pressure, high temperature range, and tuneability of ionic interaction, which make them applicable in a range of applications. It extends to nanofluids, engineered through nanoparticles’ dispersal in base fluids, for enhanced thermal conduction, overall thermal performance, and stability. It takes into consideration, in addition, nanomaterials’ extraordinary properties, including high specific surface, quantum confinement, and enhanced mechanical stiffness, and its role in spurring development in a variety of industries, including biomedical engineering and catalysis. There is a critical review of advanced characterization techniques, including spectroscopic analysis, electron microscopy, calorimetry, and scattering, in an attempt to expose structure-property relations in such materials. There is a consideration of how such methodologies have helped expose synergy between ionic liquids, nanofluids, and nanomaterials and pave the way for new, emerging, and innovative applications in materials, electronic, and energy industries. There is a conclusion with a consideration of emerging trends and future directions in the field, with a view to underlining synergistic experimental and theoretical approaches’ role in spurring development in the field.