Control all of your Hatcheries from a single building. You add monsters to add one build queue and it sends instructions to whichever Hatchery becomes available first.
The Hatchery Control Center or, HCC gives you control over all your Hatcheries. It also allows you to see when your housing will be full so you better plan your monster army. Clicking and holding on a monster adds it to the queue. Each queue slot can hold up to 20 monsters, allowing you to have a total of 145 monsters queued up at any time. The monster in the first queue slot will be sent to whichever Hatchery becomes available first. If you click on a monster on the queue or in a Hatchery it will be removed/canceled. You can see how much space you have in your Monster Housing and how much space the monsters in the queue will take up when finished. You can add more monsters to the queue than you housing can hold. They'll just wait in the Hatcheries for more housing space to become available.