Conversion of waste heat into electrical energy via thermoelectric technology requires highly efficient thermoelectric materials. Developing thermoelectric materials with high efficiency is becoming an important area of research to develop alternative energy technologies to reduce our dependence on fossil fuels and reduce emissions of greenhouse gas. In this presentation, an overview of various TE phenomena, materials developed so far, several key parameters involved in thermoelectric research with their current applications will be discussed. Potential thermoelectric such as half-Heusler, Zintl phase Mg3Sb2 compound, SiGe, Mg2Si and Cu2Se will be presented in terms of challenges in their processing, optimization of TE properties and their applications. Fundamental understanding, unresolved issues related to carrier transport and highlight the present research resolving these issues for emerging a next generation of efficient bulk nanostructured materials will also be the part of this presentation.