My understanding is that they come partially assembled in the same manner as bikes get delivered to bike shops. So you have to cut the packing material away; put in the pedals, seatpost (seat already attached), stem (bars and levers already attached), wheels (tires/tubes installed), and skewers; adjust derailleurs, brakes, bottom bracket, headset, bars and saddle; check tightness on all fasteners; maybe cut and reinstall cables and housings.