Yesterday NASA released images and a video of a major hot-fire testing of 2 rocket engine injectors which are completely 3D printed. The injectors, which are responsible for mixing hydrogen and liquid oxygen to produce an incredible 20,000 pounds of thrust, performed perfectly. By 3D printing the injector, they were able to build the part in just 2 pieces, as opposed to 162 they would have needed if they were using traditional manufacturing methods. More details on this story can be found here: http://3dprint.com/13392/nasa-rocket-3d-print/

Below is a picture of NASA's hot-fire test of one of the 3D printed injectors: