The circular economy holds the promise of a zero-waste future, yet formidable challenges in technology, finances, and regulation persist. How will governments and businesses overcome these obstacles to achieve true sustainability?

4D printing adds a new dimension to 3D printing: time. An object changes its shape or quality as it encounters some external stimuli, such as temperature shifts or contact with water. Currently, research in several laboratories, 4D printing may add programmability to materials and objects.