For a long time, it has been deemed impossible to combine light and magnetism because of the frequency gap. Optical waves oscillate orders of magnitude faster than the spins of charges, which means that it is not simple to have them interacting. Nevertheless, the idea to harness light and magnetism has intrigued physicists and chemists during the last 50 years. This research direction became a real possibility after the development of femtosecond laser sources and ultrashort light pulses, which can be used as either external stimuli or ultrasensitive probes in advanced experimental physics. With this approach, it is possible to excite magnons, i.e. the collective oscillations of spins (the intrinsic angular momenta of electrons), which are able to carry, transfer and process information with extremely reduced energy consumption and, at the same time, to push the speed of information processing towards higher limits (THz frequency range). Concurrently, one particularly efficient way of capturing and manipulating free-space light and couple it to the nanometric scale at which magnons oscillates is to exploit plasmonic devices. These nanostructures exploit the collective motion of electrons (plasmons) in electromagnetically coupled elements tailored from composite materials to design the so-called metamaterials. In ULTRON we aim to study the plasmonic and magnetic properties of metamaterials supporting both plasmonic and magnonic excitations by using ultrashort light pulses. We target to obtain a coherent hybridization of plasmons and magnons, in a quite-unexplored frequency range: the mid-infrared (3-30 µm – 100-10 THz), where the frequency gap between these collective excitations is also extremely reduced. In this way, it will be possible to connect in an unprecedented way light with magnetism, since plasmonic oscillation will be spatially and temporally superimposed with spin waves, thus enabling a coupling between the two types of excitations. ULTRON will disclose a mechanism which might have a huge impact on forthcoming light-driven deterministic (coherently-controlled), ultrafast (sub-ps regime) and ultra-dense (tens of Tb per inch2) data processing nanotechnologies based on plasmon-mediated hybridization of photons and spins, thus making real the possibility to integrate magnonics with light-based technologies working at even higher speeds than electronics.