Transparent conducting oxides (TCO) are well known for their unique opto electrical property and technologically been used in thin film form for more than 50 years as essential components of many optoelectronic devices such as flat panel displays, transistors, sensors, liquid crystal displays, solar cells, energy efficient window system etc.Various deposition techniques like CVD, PVD, spray pyrolysis, etc are usually adopted for its fabrication. Sol-gel deposition of TCO thin films is nowadays one of the most promising technologies because it is relatively less expensive and easy to adopt. This book contains a brief overview of TCOs, their structural feature, electrical and optical properties, thermal emittance, conduction mechanism, sol-gel fabrication along with a brief literature survey on the earlier work of TCO films.