For 3-D food printers, chocolate is a good material to start with, because it's fairly simple to make it liquid inside the printer cartridge and solid once it drops out. Courtesy of Smart Gastronomy Lab, University of Liège hide caption

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Cambrian Genomics says that what it calls a DNA printer is essentially a DNA sorter — it quickly spots and collects the desired, tailored stretch of DNA. Courtesy of Cambrian Genomics hide caption

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Liam Gaynor (center), 8, and Laura Stark (right), 8, watch as an object is made on a 3-D printer at the Hillsdale (N.J.) Public Library in January. Michael Karas/North Jersey/Landov hide caption

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Artists in the residency program at Autodesk are given access to production-quality equipment in workshops, allowing them space to create at-will. Blake Marvin/Courtesy of Autodesk hide caption

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International Space Station Commander Barry "Butch" Wilmore holds up the first object made in space with 3-D printing on Nov. 25. NASA hide caption

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Army researchers will try to find ways to 3-D print nutritious food with less heavy packaging than the current military meals. Aarti Shahani/NPR hide caption

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Garrett shares a moment with his mother, Natalie Peterson. "He has been doing so good," she says. "He's been smiling." Nicole Haley/University of Michigan Health System hide caption

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H. Jerry Qi, associate professor of mechanical engineering at Colorado University, holds simple models printed using polymers that have "shape memory." The flat piece on the left can reshape itself into a box with the application of heat. Glenn J. Asakawa/University of Colorado hide caption

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This riboflavin-rich material can be used to print intricate, microscopic structures in three dimensions. Courtesy of North Carolina State University hide caption

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