The Internet of Things (IoT) is shaping the evolution of the future Internet. According to the vision underlying the IoT, the next step in increasing the ubiquity of the Internet, after connecting people anytime and everywhere, is to connect inanimate objects. By providing objects with embedded communication capabilities and a common addressing scheme, a highly distributed and ubiquitous network of seamlessly connected heterogeneous devices is formed, which can be fully integrated into the current Internet and mobile networks, thus allowing for the development of new intelligent services available anytime, anywhere, by anyone and anything. Many applications with high social and business impact fall under the IoT umbrella, including personal healthcare, smart grid, surveillance, home automation, intelligent transportation, while it is expected that new ones will emerge once the enabling technologies reach a stable state. At the moment, four of the most important challenges are: i) Architectures, protocols and algorithms for an efficient interconnection of smart objects, both between themselves and with the (future) Internet within the 5G context; ii) The creation of value-added services in cross-domain applications, especially open and interoperable, enabled by the interconnection of things / machines / smart objects, in such a way that they can be integrated with current and new business and development processes; iii) The support of a virtualized IoT based on the concepts of virtualized components and functions within dense and heterogeneous environments; iv) Security, privacy and trust in the IoT applications, for ensuring that the provided services will protect the users’ data, provide guarantees that no malicious users/devices will affect the system decisions and that the IoT applications will be secure and privacy-preserving “by design”.