This book introduces the basics of the Internet of Things (IoT) and explores the foundational role of sensors in IoT applications. The IoT is a network of devices and objects: sensors, actuators, hardware, software, human beings, domestic appliances, health monitoring equipment, and other things connected to the internet, which is designed to operate in a coordinated fashion to receive, process, and interpret signals and take appropriate action. It provides a seamless real-time interface between the physical and digital worlds by integrating sensors with networking, computation, and actuation facilities. This book sketches a perspective of the IoT with sensors as the focus of attention. Diverse applications of the IoT that are destined to make an impact on our everyday lives in the near future are discussed. It presents a comprehensive overview of the most recent sensor technologies used in the IoT to keep the reader abreast of the current advances at the frontiers of knowledge. The book will cater to student and professional audiences, and will be useful for postgraduate and Ph.D. students studying physics, engineering, and computer science as well as researchers, engineers, and industrial workers engaged in this fast-progressing field.