Awards and recognition: Stefano Covino was PI of the optical polarimeter equipping the Italian “Telescopio Nazionale Galileo”. He served as chair of the European Southern Observatory committee. He was also member of the “Istituto Nazionale di Astrofísica” Scientific Council. He has been PI of several tens of different observational projects at the main ESO telescopes.

Abstract：The direct detection of gravitational waves has definitely been one of the most exciting discoveries of the decade. An exceptional technological and scientific achievement that heralded the birth of gravitational astronomy. The discovery of an electromagnetic counterpart, the so-called kilonova or macronova, came partly unexpected a few months ago and generated one of the most intense observational campaigns ever carried out. We today quickly review the hectic days after the detection of GW170817 and, almost simultaneously, GRB170817A, with the identification of the optical counterpart, named AT2017gfo. The intense spectro-photometric coverage secured by the main facilities worldwide showed a transient never observed before and remarkably consistent with numerical relativity simulation predictions. Observations at low and high energies allowed us to characterize the associated, atypical, short GRB. We discuss how the rapid color evolution of the transient is interpreted, the evidence of r-process nucleosynthesis, the geometric information about the system, and mention some of the most exciting perspectives for the future of this research field.