“Neil Gershenfeld, a physicist and computer scientist who runs the Center for Bits and Atoms at MIT, envisions a time when many of us will have a “fabrication center” in our homes. We’ll be able to download a description of, say, a toaster — perhaps one we designed ourselves — to our computers, and then feed the designs and the raw materials into a personal fabricator. At the push of a button, almost like hitting “print,” the machine will spit it out.”