The hatchery is the building you'll start off with when choosing the zerg, and it is the only building you'll be able to produce units from. All the other zerg structures are either for defense, upgrades, or to provide the genetic support nessessary to create different units at the hatchery. Hatcheries produce up to 3 larvea at a time, each, allowing you to create masses of new warriors very quickly. The hatchery itself includes one upgrade, the ability to burrow. All zerg land units, with the exception of the ultralisk, can burrow undergound and be invisible to enemy units without a detector.Try to create many hatcheries to help multiply your production speed. Also, remember to place new hatcheries as close as possible to new mineral expansions, ensuring an efficient mining rate.

Extractors are the zergs' only way to convert raw vespene gas into a useable form. The Zerg don't use the gas a fuel, like the other races. Instead, they need the vespene gas to power their accelerated metabolisms. All upgrades and warriors more powerful than a zergling requires this resource. The extractor costs half as much as the other races' gas refineries-just 50 minerals. Only one drone can be in the extractor at a time, so there is a limit on how many can effectively gather from it. Usually three or four drones is the most you want, depending on how far your hatchery is from the extractor.

Creep colonies are structures that add to the creep created initially by your hatchery, providing more space for buildings or more creep colonies. These creep colonies, once you have the other appropriate structures, can mutate into defensive structures capable of either firing at air or land targets-yep you have to choose one, and the mutation is irreversable once complete.                                                                                          

The Spawning pool is the first in the line up of zerg tech buildings. It allows the production of zerglings at the hatchery, as well as the metabolic boost upgrade that doubles the zerglings run speed. Later, with the upgrade of the hatchery into the Hive, the adrenal gland upgrade becomes available. This upgrade doubles the zerglings vicious attack speed. The spawning pool also provides the DNA structure nessessary to upgrade the hatchery into a lair, and it allows the mutation of the next level tech building-the hydralisk den. With the spawning pool handy, a player can mutate a creep colony into a sunken colony, a building for stationary ground defense. 

The Hydralisk den allows the production of the awesome hydralisk species at the hatchery. At the hydralisk den you can upgrade your already-formidable hydralisks with faster running speed and added firing range. After you mutate the hatchery into a lair, you can obtain the lurker aspect upgrade for your hydralisks. This upgrade turns your hydralisks (only on your command of course) into the devastating lurker unit.

The Evolution Chamber doesn't give access to any new fighting units, but it is still an essential part of any brood. With the evolution chamber available, you can mutate your sunken colonies into spore colonies; buildings that have built-in detectors and fire at air units within their attack range. At the evolution chamber, you can upgrade the armor, melee, and ranged attack values of your ground units. You'll need to mutate your hatchery into a Hive before you can upgrade your units to the maximum level, but the first level is available from the start. It is more effective if you have three evolution chambers to upgrade all aspects of your army at once, providing you have enough resources.

Once mutated from a creep colony, sunken colonies are the zerg form of stationary defense against ground units. The sunken colony sends a huge tentacle undergound only to break the surface and impale some poor invader. It does reasonable damage of 40 hit points per pop, so don't underestimate the value of this building. The sunken colony continues to uphold the creep, but it cannot fire back when attacked by air units. Also, too many sunken colonies can be a waste of money and time, because they can be countered with long range attacks. It may be wise to only keep enough around to backup your base defense should the enemy decide to attack in force.

Spore Colonies are the sunken colonies for the air. They fire upon air units that happen into their attack range, and they also have a detector built it, making cloaked aircraft uneffective. Use some spore colonies to defend against air units where using hydralisks or mutalisks is cost prohibitive. They also come in handy for detectors around your sunken colonies. It may be a good idea to mix sunken and spore colonies together to provide defense against both forms of attack. But like the sunken colony, the spore colony has a flaw; it can't defend itself when attacked by a ground unit.

The lair is the upgraded form of the hatchery. They still produces three larvae apiece, but it also sports more hits points and the three upgrades for your overlords-the sight range upgrade, the essential speed upgrade (it is essential because the overlord crawls without it) and the ventral sac upgrade that allows your overlords to transport ground units. With a lair, you can now start the second level zerg units, buildings and upgrades.

The Spire allows you too mutate your larvea into basic air units of the zerg, including the mutalisk, and the scourge. Also available upon construction of a spire is the air attacks and armor upgrades. These upgrades increase the attack and defense values of your air units. You cannot achieve the highest level of attack and defense until you have mutated your spire into the greater spire. But before you can mutate the spire, you must have one of your lairs mutate into a Hive.

The queens nest allows the production of the zerg queens at the hatchery. It also provides three upgrades for the queen including the spawn broodling ability, the ensnare ability, and the queens energy upgrade. For details on these abilities, check out the Zerg unit page. Even if you're not going to produce queens, the nest is essential because it allows you to upgrade your liar into a Hive-giving you access to the highest level zerg units and buildings.

The Hive is the highest level for the hatchery. Once again, it still produces three larvae do to your bidding, but it comes with additional hit points for more protection. With the Hive mutated, you can select the level three carapace and attack upgrades, as well as construct the high level zerg tech buidlings such as the greater spire, the ultralisk cavern, and the defiler mound.

The Greater Spire is mutated from the spire. Its comes standard with more hit points than that of a normal spire, and it allows you to upgrade your air attackers' abilities to the highest level. It also gives you the option of mutating your mutalisks into the powerful guardian and devourer units, the specialty air attackers of the zerg.

The Ultralisk cavern gives you access to the awesome ultralisk unit. It also allows you to upgrade their defense and speed values dramatically, but other than that, building doesn't have many other uses.

The defiler mound gives the larvae the DNA information needed to mutate into the devastating defiler unit. The defiler mound also provides the Consume and Plague ability upgrades, as well as a energy reserve upgrade.