WE PROPOSE TO USE STATE-OF-THE ART NUMERICAL SIMULATIONS OF NSBH AND NSNS MERGERS AND OF THEIR POST-MERGER REMNANTS TO INFORM OBSERVATIONS OF THESE SYSTEMS. WE WILL FOCUS ON PREDICTING THE PROPERTIES OF THE EJECTED MATERIAL A CRITICAL STEP IN THE MODELING OF KILONOVAE AND IN THE DETERMINATION OF THE IMPACT OF MERGERS ON THE ENRICHMENT OF THE UNIVERSE IN HEAVY ELEMENTS. A BIG CHALLENGE IN MODELING THESE OUTFLOWS IS THAT THEY ARE PRODUCED OVER A WIDE RANGE OF TIME SCALES. MATERIAL IS FIRST EJECTED DYNAMICALLY DURING THE MERGER (OVER A FEW MILLISECONDS) THEN THROUGH POWERFUL DISK WINDS (OVER 100 MS) AND FINALLY THROUGH THE VISCOUS EVOLUTION OF THE REMNANT ACCRETION DISK (OVER 10 S). WE WILL PERFORM FOR THE FIRST TIME 3D SIMULATIONS CAPABLE OF CAPTURING ALL THREE COMPONENTS OF THE EJECTA WITH SELF-CONSISTENT EVOLUTION FROM BEFORE THE MERGER UNTIL MASS OUTFLOWS BECOMES NEGLIGIBLE.