MIT engineer Skylar Tibbits recently spoke at a TED conference about the promise of 4D printing. The act of 4D printing creates objects in one state that could then change to a different state over time. Without human intervention, the object alters its shape based on moisture or heat from a given environment. A 3D-printed straight line, for example, could form a cube when submerged in water. While 4D printing is still theoretical, Tibbits envisions scenarios where 4D structures assemble themselves in harsh environments without the need for humans to risk their lives.