Printing images is easy. Just select an image of a purple robot on your PC, for example, and press print. Your home printer exactly shoots drops of ink onto a flat piece of paper, creating the robot's 2-D image. "Printing" 3-D objects is different. Take the purple robot. First select a file of the 3-D printer. Immediately, the printer begins making noise, and a nozzle   releases plastic material in thin layers. In two or three hours, a 3-D purple robot is standing before you. 3-D printing has developed to the point where printers can now create high-quality objects using a variety of materials, including metals. That means 3-D printers can now make final products that meet high industrial standards. 3-D printers are already being used to make parts for racecars and jets as well as man-made limbs and hearing aids. So far, few homes have 3-D printers. That's because 3-D printing is not only new to most people but also quite expensive. To bring 3-D printing to the masses, some retail stores   plan to offer the service. For example, the Staples chain of office supply stores has announced that it will offer 3-D printing in Europe beginning in 2013. Customers will be able to submit their own 3-D designs to Staples website for printing. After the job is done, they'll pick up their item at a nearby Staples store or have it mailed to their homes. This service is sure to encourage many more people to try out 3-D printing. What do we learn about the 3-D purple robot?
How long it can usually last How it can darken its own color How it gradually takes shape How much it costs to produce