Because many chemical, biological, and physical sensors depend on interactions occurring at the nanoscale, the impact of nanotechnology on the sensor world is significant. Addressing research areas and challenges, this book describes nanosensor development from the viewpoints of materials, device structures, and functionalities. It starts from preliminary ideas and proceeds to state-of-the-art nanosensors. The book provides readers with information on the current state of nanotechnology-enabled sensors as well as their advantages, uniqueness, and limitations. It also indicates future research directions.