“The possibilities for prototyping will be greatly expanded as 3-D printing becomes widely available and affordable over the next few years. The technology, which makes it easy to sketch an idea for an object on a computer screen and then manufacture a physical version (usually made of plastic or steel), is “enabling a class of ordinary people61 to take their ideas and turn those into physical, real products,” according to J. Paul Grayson, chief executive of the design-software company Alibre. It provides just one more way to bring our questions into the physical world.”