The technology uses "smart shape memory polymers" which have the unique ability to change to another programmed shape when heat if applied. Using these polymers, the researchers were able to create complex objects that change shape in a controlled sequence by 3D printing patterns into the object. Then when its heated, it's possible to make the 3D printed object assemble itself. Previously, techniques like this required precise control of heat -- this time, heat can be applied uniformly to the object.
There are many applications for this technology. For example, unmanned drones might be able to change shape based on what its mission could be. But the most exciting application might be the ability to ship complicated objects in a tube or folded flat, and have them assemble themselves once they're at their final destination.