  Fifth generation (5G) and beyond communication systems open the door to
millimeter Wave (mmWave) frequency bands to leverage the extremely large
operating bandwidths and deliver unprecedented network capacity. These
frequency bands are affected by high propagation losses that severely limit the
achievable coverage. The simplest way to address this problem would be to
increase the number of installed mmWave base stations (BSs), at the same time
augmenting the overall network cost, power consumption and ElectroMagnetic
Field (EMF) levels. As alternative direction, here we propose to complement the
macro-layer of mmWave BSs with a heterogeneous deployment of Smart
Electromagnetic (Smart EM) Entities - namely IAB nodes, Smart Repeaters,
Reconfigurable Intelligent Surfaces (RISs) and passive surfaces - that is
judiciously planned to minimize the total installation costs while at the same
time optimizing the network spectral efficiency. Initial network planning
results underline the effectiveness of the proposed approach. The available
technologies and the key research directions for achieving this view are
thoroughly discussed by accounting for issues ranging from system-level design
to the development of new materials.
