Additive manufacturing, commonly referred to as 3D printing, is changing what is possible in rocket propulsion. What used to be hundreds of painstakingly assembled pieces, can now be printed as a single, elegant component. This is breaking down the barriers to greater engine performance, quicker time to market, and lower costs. Despite being around since the 1980s, additive manufacturing is having a renaissance, with new injections of capital leading to new capabilities and applications. Applying these findings to engine development and beyond will transform the space industry.