Additive manufacturing (AM) can be defined as the manufacturing layer by layer of parts from digital models. This new route of material processing has gained an increasing attention because of the ability to design complex three-dimensional parts without modifying the processing tool. The growing research activity on AM technologies stands from the viewpoint that several aspects are still not known for engineers and scientific communities from both the technical and scientific sides. Some of these aspects are the qualification of the parts according to standards, the link between the processing and the performance, the optimization procedures for both processing conditions and in-service properties, the response of the additively manufactured parts under severe working conditions, the development of 4D printed architectures, etc. There is no doubt that AM is now viewed as a new revolution in material processing because it combines a high degree of freedom in design and manufacturability from digital models. AM ranks as one of the major research fronts in engineering and materials science.