Underground habitats have recently become a focal point of off-planet colonization efforts. Protection from micrometeorites, radiation and other potential hazards makes underground sites desirable compared to surface dwellings. Building such subterranean structures presents a plethora of challenges, not the least of which is how to actually construct them. A team of researchers at the Delft University of Technology (TUD) is working on a plan to excavate material and then use it to print habitats. All that would be done with a group of swarming robots.