In Creatures 3 and Docking Station, each species of creature has what it considers its home. The Norns call the Norn Terrarium and Norn Meso their homes, while the Grendels and Ettins have similar feelings for the Jungle and Desert Terrariums respectively.
A place is being considered home by creatures if there is a high amount of Home Smell Cellular Automata (CA) present in the room. A creature with a high comfort drive will often try and track the CA to navigate to its home, usually to lay eggs. The Home Smells are Norn Home (CA 15), Grendel Home (CA 16) and Ettin Home (CA 17).