Transparent flexible electronics is an emerging technology which makes use of wide band gap semiconductors that can be processed at low temperatures on glass or plastic substrates. Electronic systems that cover large area and curved surfaces together with transparency bring the possibility of numerous applications that are outside the scope of rigid wafer based electronics. Flexible electronics, electronic textiles, a wearable wellness system, and sensory skin are some of the applications of flexible electronics. The key factor in the realization of transparent electronics is the development of high performance fully transparent thin film transistors. Thin film transistors (TFTs) based on transparent conducting amorphous oxide semiconductors (TAOS) such as InGaZnO (IGZO), zinc tin oxide (ZTO), zinc indium tin oxide (ZITO), etc. provide additional functionalities like transparency, high field effect mobility and potential for room temperature processing. The performance of these TAOS based TFTs are superior to their silicon (a-Si:H TFTs) and organic TFTs. Though there are monographs and books on a-Si:H TFTs and organic TFTs, a book on TAOS based TFTs is rare. This book introduces the graduate students and beginners to the field of amorphous semiconductors. The mass production of this kind of TFTs on large area substrates involves the complications associated with controlling the composition of oxide compound semiconductor thin film material. Pulsed laser deposition allows for the growth of an oxide semiconductor in a very high oxygen rich environment while co-sputtering is an effective technique for the growth of a multicomponent film and to control the film chemical composition in a systematic and easy way. These manufacturing aspects will be of interest to those working in the industry. The review on the n channel, p channel TFTs, and the detailed description on the extraction of various TFT parameters like the threshold voltage, field effect mobility, sub threshold slope and on-off ratio etc. will be ready reckoner to those working in the field of transparent electronics.