A vaso-occlusive system comprising a catheter with a working end that carries a fluid media for introduction into an aneurysm. The fluid media carries a volume of microspheres, wherein each microsphere has a sacrificial shell or coating that surrounds an interior core portion of the microsphere. The core portions of the microspheres comprise either a first or second polymerizing composition, wherein interaction of such binary compositions will cause polymerization of the media into a gel or solid media that will occlude the aneurysm. An energy delivery means is provided within the catheter working end to cause removal of the sacrificial coatings of the volume of microspheres to thereby induce the polymerization process.