[[Tyranids]] cross the [[galaxy|galaxies]] and massive voids in between in vaste '''Hive Fleets''' of millions of sentient ships.

Of the 3 major Hive Fleet invasions, two come from the Eastern fringe, but one is moving up from below the galactic plane. The ships contain everything required to sustain the fleet; some ships being purely for crushing resistance, the larger ships contain birthing pools to create the huge land armies of the Tyranids and even more ships when the need arises. This nutrients are replenished by scouring every planet conquered of every shred of biological matter, including all the Tyranids it seeded to the planet. Because the Tyranid forces are re-cycled in this way the "design" of the Tyranid warriors can be altered by genetic engineering, allowing the Tyranid forces to rapidly adapt to overcome any enemy. Further, the Tyranids absorb the DNA of defeated enemies, allowing for further genetic diversity. It is believed the [[Genestealer]] and [[Broodlord]] are derived from human DNA, the [[Zoanthrope]] from [[Eldar]] and the [[Biovore]] from [[Ork]] DNA.