Scope and Purpose Over the last 50 years, Computing Systems have successfully surfed the Moore’s law wave. Today, we observe a clear stagnation in this miniaturization race while a new generation of applications (such as Artificial Intelligence) are producing unprecedented amounts of raw data. To overcome this major challenge, new technologies aiming at revising classical Computing Architecture that are continuously moving data from the processing unit to memory are essential. Monolithic-3D technology (M3D) has the potential to improve the energy efficiency of new computing architectures. Indeed, thanks to its nano-scale Monolithic Inter Tier Via that is 100x smaller than state of the art Through Silicon Vias, M3D opens the door for new computing systems immersed in memory. Currently, there is much effort spent on M3D technology development and system-level design. Yet, numerous challenges remain. For example, the development of “cold process” to monolithically fabricate a reliable device on top of another one. Another challenge is on the understanding of the physical issues (electro-thermal) and design of energy efficient and reliable M3D systems. Ultimately, CAD tools for planar technology must be adapted for M3D to enable new computing architectures for large on-chip memory bandwidth. This special issue aims at addressing these problems to speed up the emergence of High Energy Efficient Computing Systems.