Containment units are powered stasis tanks present in the Xenoresearch Labs on Eastern SkyTown, Elysia. They were used by the Space Pirates to study Phazon Metroids, and kept several of them captive. The units are powered by Energy Cell ID: GC-9713N-5 further into the Labs. Samus finds the Seeker Missile Launcher in a containment unit next to the Energy Cell, which she must remove in order to disengage the shield and obtain the Launcher. However, this also releases the Phazon Metroids. On her way out of the Labs, Samus will encounter many shattered tanks that formerly held Metroids, as well as intact ones which were empty. With the shield down, all containment units that are still intact can be destroyed with Ice Missiles or charged Plasma Beam shots. One containment unit in Xenoresearch A Lift contains an Energy Tank, which can be obtained after the Energy Cell has been removed.
The units appear to have similar properties to glass when not protected by an energy barrier. However, the unit containing the Seeker Missile will shrink in size when attacked, making their physical properties ambiguous. It is unknown whether these units were previously installed by the Chozo or Elysians, or were installed by the Space Pirates upon their arrival.
"Containment unit online. The pod's power source is keeping the unit's energy barrier active."