The introduction of additive manufacturing from a privileged relationship between digital and physical realization is starting to transform the manufacturing industry. This attractive technology still has some drawbacks such as printing speed, surface finish of the final product and lack of fully functional materials. 4D printing is the additive manufacturing of active or smart materials with sensitivity to energy stimuli. From a perceptive system to a stimulation associated with a more or less complex structure, a 4D object is able to make the equivalent of a decision which may be revisited in future energetic interactions depending on the effects produced. 4D printing has three roots: additive manufacturing (active and passive) materials and their stimulations.