Heart of the Swarm Campaign- Umoja: Lab Rat (Part 2)

Valerian asks Kerrigan what she's doing- to which her response is simply 'putting your controlled environment to the test'.

Once the zerglings are hatched, Valerian calls for a stop and tells Kerrigan he didn't call for zerglings.  She counters that nothing involving the Zerg ever goes as planned, and Valerian's response is to call in security forces to clean out the test chambers.  Kerrigan indicates that she intends to destroy Valerian's security mechs to make a point- that the Zerg cannot be controlled.

Your immediate next step is to destroy the security robots in the next chamber over with your new zerglings- before they can destroy the containment units in there.  This should be relatively easy- and nets you roughly ten additional zerglings from the holding pens.  With that complete, Kerrigan can now sense more zerglings elsewhere in the base, in other holding pens- which she also intends to free.  These three pens now become your bonus objectives- you don't have to open them, but they'll net you additional forces, so there's very little reason not to.

Continue producing overlords as needed and creating more zerglings- you have no real restrictions here, so unless you're trying to meet a time challenge, there's no reason not to take it slow and amass a very large force of zerglings.  Particularly given the fragile nature of the things, which causes you to lose some in pretty much any fight they get into.

None of the fights here are going to require any sort of complex tactics (which is good because you can't exactly use any with only zerglings at your disposal) so just sweep through the facility and chew up anything that takes your fancy as particularly zergable.  Once the personnel are evacuated from the area and you've destroyed the Eradicator robot that is the core of Valerian's automated defenses, the mission concludes with a victory.  Valerian complains that it's lucky that no people were killed, and Kerrigan replies that luck wasn't even slightly a part of it, then sends the zerglings back to their containment cells- prompting her release from her own containment.