Zero-space, or Z-space as it is usually called, is a dimension of white nothingness, where neither time, nor space exist. It can be passed through using a certain type of technology, allowing for instant faster-than-lightspeed communication via Z-space transponder and faster then light travel. Special Z-space engines are needed on a ship for it to travel through Z-space, though one could enter it via a black hole -- if one survives. Although the Andalites discovered Zero-space, the Yeerks quickly adapted it after stealing some of their ships in The Hork-Bajir Chronicles. Z-space is also important in morphing because that is where the excess matter goes when someone morphs a creature smaller than their regular body, or matter is retrieved from there when more mass is needed, such as a human