This special issue aims to provide a timely discussion on the technical trends and challenges of circuits and systems on Internet of Things (IoT). Rapid advancement of networking technologies together with extreme miniaturization of computing and communication devices enable emerging and exciting applications and services that connect the cyber and physical worlds. In the future, digital sensing, communication, and processing capabilities will be ubiquitously embedded into everyday objects, turning them into the IoT. In this new paradigm, smart devices will collect data, relay the information or context to each other, and process the information collaboratively in a machine-to-machine (M2M) manner.