Zerg Structures
The fearsome-looking Zerg facilities are in fact semisentient organisms that live, breathe, and bleed just like anything else. Their tough, fleshy exteriors are incredibly durable and can withstand any form of attack for prolonged periods of time. Zerg structures feed on the nutrients contained in the Creep, the dense organic blanket spawned from Zerg Hatcheries. Thus all Zerg structures, aside from Hatcheries and Extractors, must be built on a layer of Creep.
Zerg structures are created through the metamorphosis of Zerg Drones, the same units the Zerg use to collect minerals and harvest Vespene Gas. Because a Drone is essentially lost when a new Zerg structure is founded, the Zerg commander must produce far more worker units than his Terran and Protoss rivals. That the sacrifice of a Drone is required for the production of any Zerg structure effectively increases each structure's cost by 50 minerals. However, since all Zerg units are generated from Larva, unlike the Terrans and Protoss, the Zerg needn't build multiple facilities dedicated to producing new units.
Much like all Zerg units, Zerg structures regenerate lost hit points at a slow yet steady rate. Though the Zerg cannot repair their injured facilities directly, given enough time, a Zerg structure even on the brink of death will recover to its full strength.
Next: Basic Zerg Structures 
