Flow measurement is a basic tool in industry, engineering and research. The existing applications reveal the evolution and development of new methods and devices through the years. Some of the latest emerging technologies, such as microelectronics and nanotechnology, have put forward new challenges in the flow measurement and are treated at the beginning of this book. This book comprises 8 chapters divided into 4 sections, starting with “microflows”, followed by the “biphasic” and “gas flow”. Fourth and the final section deals with the “indirect methods of flow measurement” involving two different applications