The internet story started in the late 1960s with a research project connecting together a bunch of computers. Since then, the Internet has grown to a worldwide network of networks, connecting billions of devices. With the development of technologies and telecommunications, many other types of devices have also joined the network, allowing any single thing to be connected to the rest of the world; the Internet of Things (IoT) was born.  Everybody has heard of so-called smart devices: smart watch, smart meter, smart lights, smart home, smart cities… What makes those things or environments ‘smart’ is their capacity of processing data and communicating and interacting with their environment, entering the world of sensors and actuators.  In many cases, smart worlds rely on small, constrained devices, with limited processing power, communication bandwidth and power supply. This raises new challenges in the design of those information systems, and new hybrid models have to be conceived, allying decentralized simple devices with specific network technologies and centralized, often cloud-based, services that control the whole environment and make decisions, thus justifying the term ‘smart’. Internet of Things not only raises technological questions. It also poses new challenges in regards with security, data privacy, system resilience… In this learning path, we will introduce the different concepts of the IoT, illustrating them with a set of use cases. We will also review the technical and societal challenges it raises, and that any citizen should be aware of, since our lives are all getting deeply impacted by these smart systems.