Severe environment survivability is the key matter in the development of new space/energy-based applications of smart nanomaterials. They must exhibit excellent physical properties accompanied by lightweight, reusability, and multifunctional capabilities, along with processes that involve either low-energy consumption or a highly efficient method of energy storage, conversion, or production. Our chapter presents a scientific and technical discussion related to the smart nanomaterials, as well as nanocomposites that reflect the need for lightweight materials with potential multifunctional, self-healing, or smart capabilities. Additionally, the chapter focuses on smart nanomaterials for space applications, including metal/oxides/selenides nanoparticles, quantum dots, nanowires, and nanotubes and their composites exhibiting multifunctional properties. We introduce not only the synthesis, properties, modifications, but also the various applications in photovoltaics, batteries, hydrogen storage, and supercapacitors, and energy applications of smart nanomaterials, which focus on their synthetic methods, including sol/sol-gel, hydro/solvothermal, oxidation, deposition, sonochemical, and microwave-assisted approaches.