Wireless RF energy transfer in the massive IoT era : towards sustainable zero energy networks In this chapter we overview massive Internet of Things (IoT) and recognize how the IoT revolution spans beyond technology encom passing many societal aspects. We provide some illustrative examples of the sheer volume of connections in massive IoT deployments. To do so we identify essential use cases together with their requirements and key per formance indicators (KPIs). We discuss how these requirements and KPIs impact the development of novel techniques and technologies. Moreover we overview the current state of the art and pin point key technologies for massive IoT. We then present enabling methods and technologies that are fundamental for the development of sustainable information and com munications technology (ICT). We examine the power problem in massive IoT. Finally we argue that massive WET is instrumental in i) addressing the challenges of powering massive IoT deployments ii) reducing electronic waste and iii) building sustainable ICT and society