Just when 3D printing was starting to sound less futuristic, 4D printing has added a new twist. Like 3D printers, the new printing technology turns blueprints into three-dimensional objects by building them up, layer-upon-layer. But unusual materials, designs and external stimuli such as heat, electricity, a magnetic field or water give 4D-printed objects the ability to shape-shift into something new. Practically speaking, this new printing technology could one day lead to airplane wings that morph for take-off and landing, soft robots that can squeeze into and out of tight places, implantable biomedical devices that can maneuver through a blood vessel and even organs for patients in need of a lung, heart or kidney. Although still in the research stage, 4D printing is set to transform the future.