The era of Gravitational Wave (GW) Astronomy started on September 14, 2015, with the first observation of GWs from the merger of a binary black hole (BBH) system by the Advanced LIGO detectors. Two years later, on August 17, 2017, the detection of GWs from a binary neutron star merger by the Advanced LIGO and Advanced Virgo network and of the associated electromagnetic signals marked the birth of multi-messenger astronomy with GWs, opening a new chapter in the study of the universe. Besides these two observations, the LIGO and Virgo collaborations reported the detection of other 9 BBH mergers during the first two observing runs. On April 1st, 2019 the third observing run, O3, has started, and both Advanced LIGO and Advanced Virgo are operating with improved sensitivity. Several GW candidate events have been observed and other GW (and possibly multi-messenger) detections are expected in the near future. We present the preliminary results of the first six months of O3 and the prospects for future science runs.