This lecture covers the use of thermopiles in micro sensors, focusing on their sensitivity, signal-to-noise ratio, and thermal insulation. It explains the importance of thermocouple junctions deposited on a membrane to measure incident radiation heating. The lecture also discusses the impact of thermal noise in resistors, the optimization of materials for thermopiles, and the measurement techniques such as infrared pyrometry and optical pyrometry. Additionally, it addresses the correction of ambient temperature effects and the structure of thermopile sensors, including the use of MEMS technology for thermal insulation.