I've written previously about pre-fab houses, especially as they are so well suited for building in Scandinavian climates. With such a short building season, it's a huge advantage to be able to maximise building time in the summer.
Our own house- and our shed- weren't really pre-fab, but rather kit houses. All of the parts and pieces were supplied, but there was still significant assembly required. A true pre-fab simply requires connecting large pieces to produce a fully finished product. And a pre-fabricated house is by can be quite luxurious, with the Huf House being a well-known example.
The video above shows that idea taken to its extreme. A 30 story hotel was built, start to finish, bare ground to occupancy, in 15 days! An article on treehugger gives details. Each floor is finished, down to the floor tiles, light switches, window shades, etc., and is assembled on a single pallet. A crane lifts it up, the floor is laid, the windows and walls are put up, and the next floor arrives to be installed above it.
It appears there aren't any corners cut, either. Modern energy-saving technologies are built in; its earthquake resistance has been tested, even furnishings and light fixtures are ready to go. This system is said to be accurate to 0.2 of a millimeter, which is about a hundred times more accurate than my own building efforts!
I liked the comment that these kinds of systems mean that even construction can be exported. Today we buy iPads from Chinese factories; perhaps soon, we'll be buying our houses there, too.