Autoclave Aerated Concrete: Building Material for New Millenium?

What is autoclaved aerated concrete and why is a New Jersey university professor describing it as an excellent material for rebuilding the hard-hit New York metropolitan region from Super Storm Sandy? The material, best known as AAC, has been heralded as the building material of the new millennium. It's a lightweight, easily-crafted manufactured stone, strong enough to withstand earthquakes and hurricanes when reinforced with steel.