The introduction of nanotechnology opened new horizons previously unattainable by thermoelectric devices. The nano-scale phenomena began to be exploited through techniques of thin-film depositions to increase the efficiency of thermoelectric films. This chapter reviews the fundamentals of the phenomenon of thermoelectricity and its evolution since it was discovered in 1822. This chapter also reviews the thermoelectric devices, the macro to nano devices, describing the most used techniques of physical vapor depositions to deposit thermoelectric thin-films. A custom made deposition chamber for depositing thermoelectric thin films by the thermal co-evaporation technique, where construction issues and specifications are discussed, is then presented. All the steps for obtaining a thermoelectric generator in flexible substrate with the custom deposition chamber (to incorporate in thermoelectric microsystems) are described. The aim of thermoelectric microsystem relays is to introduce an energy harvesting application to power wireless sensor networks (WSN) or biomedical devices. The scanning probe measuring system for characterization of the thermoelectric thin films are also described in this chapter. Finally, a few of the prototypes of thermoelectric thin films (made of bismuth and antimony tellurides, Bi 2 Te 3 Bi2Te3 , and Sb 2 Te 3 Sb2Te3 , respectively) obtained by co-evaporation (using the custom made deposition chamber) and characterized for quality assessment are dealt with. All the issues involved in the co-evaporation and characterization are objects of analysis in this chapter.