Tech lab

The tech lab is a terran add-on in StarCraft II. It allows attached production structures to build advanced units, and provides some upgrades for those units.

A structure may not be attached to both a reactor and tech lab simultaneously.

Overview
The tech lab provided the advanced facilities needed to store the medpacks used by medics. During the Second Great War, Remedius Medical Systems developed a medpack storage facility that could be placed within barracks without the need for a tech lab.

In Wings of Liberty
In StarCraft II: Wings of Liberty, tech labs can be upgraded to double as a reactor. This costs 25 protoss research points. Also, tech labs only serve to allow you to build the more advanced units. Upgrades that are normally researched through the tech lab in melee games are instead researched in the armory on the Hyperion and some are already pre-researched (such as the banshee's cloak and the siege tank's siege mode).