Nanotechnology is an emerging interdisciplinary technology that has been booming in many areas during the recent decade. The concept of nanotechnology has been started about for the last half century ago and it has already been established its potentiality in various great areas such as nano-solar cells, electronics, optics, nanocomposites, nanosensors, superconductivity, tissue engineering, drug delivery, magnetic targeting, hyperthermia treatment for cancer, antibacterial, bioimaging, and so on. The purpose of this Book is to address key topics regarding synthesis, characterization, property studies and applications of nanostructures to meet the demand for international researchers that integrates all aspects of science and technology research. In the present book, chemical deposition methods of thin films were explained with their proper mechanism, simultaneously we explain the basic parameters behavior of thin film gas sensors and thin film characterization techniques.