High spectral efficiency is the holy grail of wireless networks due to the well-known scarcity of radio spectrum. The successive introduction of advanced communication techniques enabled by the massive increases in processing power over the last few decades has enabled a progressive rise in link spectral efficiency, which in emerging systems seems to be approaching its limits.It is becoming increasingly clear that major new improvements in spectral efficiency of wireless networks will have to entail addressing inter-cell interference. While up to recently there seemed to be no way out of the apparent end of the road in spectral efficiency growth, the emerging approach of Interference Alignment (IA) – coming out of a very recent DARPA-funded project in the US – has cast new light in the spectral efficiency prospects of wireless networks: it promises new degrees of freedom that allow more parallel transmissions to take place within the same spectrum and free of interference from each other. The HIATUS proposal constitutes probably Europe's first collaborative effort to explore the true potential of this approach in wireless networks, with the goal of making it a strong enabler for ultra-efficient wireless communications in Europe and beyond. The main objectives / challenges of HIATUS will be 1) to unveil the available degrees of freedom in a number of relevant wireless networking paradigms; 2) to explore ways to overcome the need of perfect channel state information (CSI) of all participating users; 3) to identify realistic network architectures / transmission methodologies that offer unprecedented spectral efficiency gains and 4) to provide a proof-of-concept demonstration that will convincingly show the value of the new approach, paving the way for ultra-spectrally-efficient future wireless networks.