Additive manufacturing (AM), commonly known as three-dimensional (3D) printing or rapid prototyping, has been introduced since the late 1980s. Although a considerable amount of progress has been made in this field, there is still a lot of research work to be done in order to overcome the various challenges remained. Recently, one of the actively researched areas lies in the additive manufacturing of smart materials and structures. Smart materials are those materials that have the ability to change their shape or properties under the influence of external stimuli. With the introduction of smart materials, the AM-fabricated components are able to alter their shape or properties over time (the 4th dimension) as a response to the applied external stimuli. Hence, this gives rise to a new term called ‘4D printing’ to include the structural reconfiguration over time. In this paper, recent major progresses in 4D printing are reviewed, including 3D printing of enhanced smart nanocomposites, shape memory alloys, shape memory polymers, actuators for soft robotics, self-evolving structures, anti-counterfeiting system, active origami and controlled sequential folding, and some results from our ongoing research. In addition, some research activities on 4D bio-printing are included, followed by discussions on the challenges, applications, research directions and future trends of 4D printing.

Additive manufacturing (AM) has brought about a revolution in the way we can manufacture complex products with customized features. AM has paved its way in the application areas ranging from aerospace, automotive, consumer to biomedical. AM of composites has attracted special attention due to its promise in improving, modifying, and diversifying the properties of generic materials through introducing reinforcements. This review provides a detailed landscape of fiber‐reinforced composites processed via AM techniques. Different AM processes, various material formulations, and strengths and drawbacks of AM methods are discussed. Emphasis is paid to AM techniques focusing on continuous fibers, as they hold the promise of becoming the next‐generation composite fabrication methodology. The article also tries to identify the potential of AM technology for fiber‐reinforced composites and delves into challenges facing the area.