You may recall our post on NASA's plan to use 3D printed parts to replace conventionally-made parts in future rocket engines? It's much further along than you'd think - the video below shows an actual test firing of a prototype rocket using a 3D printed liner. This, as far as we can tell, is the first time a real rocket engine has been fired with 3D printed parts.
NASA Marshall says:
This video gives you a blazing view of the one of the first tests of a 3-D printed rocket injector on June 27, 2013, in Test Stand 115 at NASA's Marshall Space Flight Center in Huntsville, Ala. Propulsion engineers used the tests to compare the performance of a 3-D printed rocket injector to an injector made with multiple parts and traditional welds. During the extreme temperatures and pressures of the hot firing, the 3-D printed part performed as well as the traditionally manufactured part. This test included a 3-D printed liner.
Yes, it really works.