Underfloor heating and self-levelling to get the floors ready for tiling... electric is good if you don't want to wait lots of time for the floor to heat up and if you've limited height to raise the floor levels...
then first of two layers of self levelling: 1. to set in and hold the heat mat and 2. to bring the floor to a smooth flat surface ready to tile (this one poured as continuously and quickly as possible to ensure there are no joins or lumps).