Dr. Berok Khoshnevis, a professor of multiple engineering disciplines at the University of Southern California and director of the Center for Rapid Automated Fabrication Technologies, dreamt up a way to print things of larger size and, arguably, importance. His company, Contour Crafting has, or will have soon enough, the capability to quickly print out walls, houses, buildings, and, conceivably, entire neighborhoods. The technology is not unlike the additive machines on the job today for smaller tasks. But instead of plastic, it uses a special cement. A trowel shapes that special cement as it emerges from the printer’s nozzle. That and a hardener added to the cement allow each layer of a wall to be applied without the usual drying delays. With his process, a 2,500 square foot custom designed home could be printed in a matter of 20 hours. That includes the walls, floors, and roof as well as conduits for electricity and plumbing. The speed and simplicity of production make the technology ideal for the erection of houses for the needy at disaster sites, and slums around the world.