3D printing of habitats made out of Moon dust.
The modern version of an adobe hut.
That will not end well. It's very difficult to keep 3D printer extruders free of contaminants. The problem with Moon dust is that it gets into everything and chews it up. Like sandpaper grit. The astronauts complained about it. They'd be better off nuking the surface of the Moon (yeah, that'll go over well) and then mine the hardened material after it cools.