Perovskites and double perovskites are fascinating materials with unique properties that make them highly versatile in a range of applications. N. Aparnadevi has conducted extensive research on the properties of these materials, exploring their crystal structures, magnetism, optical and transport properties, and their potential for use in energy materials, thin films, solar cells, and electronic devices. One of the key features of perovskites and double perovskites is their crystal structure, which is based on the ABX3 structure. This structure consists of a central B-site cation surrounded by an octahedral array of six X-site anions. The A-site cation can be a variety of different elements, and this variability allows for the tunability of properties in these materials. The magnetism of perovskites and double perovskites is of particular interest to N. Aparnadevi, who has studied their magnetic anisotropy, ferromagnetism, antiferromagnetism, and multiferroicity. These materials exhibit a range of magnetic properties, making them promising candidates for spintronics applications. The optical properties of perovskites and double perovskites are also highly interesting, with their band gaps and defect chemistry playing important roles in determining their behavior. N. Aparnadevi has investigated these properties, including the use of Raman spectroscopy and Mössbauer spectroscopy to analyze their electronic structure and spin-orbit coupling. Perovskites and double perovskites also exhibit interesting transport properties, including magnetotransport and ion conductivity. These properties make them useful in applications such as perovskite solar cells, optoelectronics, oxide electronics, and magnetic materials. Furthermore, perovskites and double perovskites have potential for use in catalysts, thermoelectricity, and phonon transport, as well as in the development of topological insulators and quantum materials. Overall, N. Aparnadevi's research on the properties of perovskites and double perovskites highlights the importance of these materials in a range of applications. With their unique properties, crystal structures, magnetism, and transport properties, these materials have the potential to transform a range of industries and technologies.