Saving energy in the building sector and automotive industry is a major global socio-economic target in energy efficiency as well as from environmental viewpoint. Electrochomic smart windows are the future of the building envelope. It allows people to dynamically control the heat and light flow into a building depending on the needs of the occupant and the changing outside environment. NiO has been studied intensively for used as an active material for anodically coloring electrode in electrochromic devices. The potential application of nanostructured material depends upon its properties. It is possible to dial-in the properties by judiciously controlling the dimensions and aspect ratio. In this book we have reported synthesis of 0D nanoparticle, 2D nanosheets and 3D nanoflowers by simple, cost effective chemical and electrochemical methods. The nanostructured morphology of NiO thin film showed a positive impact on enhancing the EC parameters required for smart window applications