Display omitted Additive manufacturing (AM), also known as additive manufacturing, permits the fabrication of fully customized objects with a high level of geometrical complexity at reduced fabrication time and cost. Besides metals and ceramics, polymers have become a widely researched class of materials for applications in AM. The synthetic versatility and adaptability, as well as the wide range of properties that can be achieved using polymer materials, have rendered polymers the most widely employed class of materials for AM methodologies. In this review, the basic principles, considering the printing mechanism as well as the advantages and disadvantages, of the most relevant polymer AM technologies are described. The particular features, properties and limitations of currently employed polymer systems in the various AM technology areas are presented and analyzed. Subsequently, 4D printing, that is the fabrication of 3D printed structures that are cabable to change with time, is discussed. A brief description of the polymeric materials and technologies under development for 4D printed structures as well as the different shape changes explored are presented. Finally, based on the characteristics of the polymers employed for each technology illustrative examples of the principal applications are discussed.