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

itoggle caption Nicole Haley/University of Michigan Health System

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

itoggle caption Glenn J. Asakawa/University of Colorado

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

itoggle caption Courtesy of North Carolina State University

Kaiba Gionfriddo, who breathes with help from a splint created by a 3-D printer, plays with his family dog, Bandit, at his Youngstown, Ohio, home. Mark Stahl/AP hide caption

itoggle caption Mark Stahl/AP

A screenshot shows how a team would track changes to its rocket project on a Sunglass platform. Sunglass hide caption

itoggle caption Sunglass

Larry Bonassar shows off an ear that he and his colleagues at Cornell University built out of living cartilage cells with the help of a 3-D printer. Lindsay France/Cornell University Photography hide caption

itoggle caption Lindsay France/Cornell University Photography

A 3-D printed bust of Yoda is one of the more popular digital designs shared on Thingiverse. Courtesy of StruveDesigns.com hide caption

itoggle caption Courtesy of StruveDesigns.com