Restricted Laboratory

The Restricted Laboratory was located on the Restricted Zone of the Biologic Space Laboratories research station. It is at the bottom of the Main Deck, in Sector 6 (NOC), connected to Sector 1 (SRX) and is designed to be detached in case anyone discovered the work inside there. The Galactic Federation designed it to house the captive-bred Metroids; these Metroids were created from the DNA of the last Metroid.

When Samus Aran discovered it, an alarm was set off, repeating the words "No entry without authorization." Unable to enter, Samus left and ran into B.O.X., finishing it off after an earlier encounter in Sector 3. After defeating it, Samus absorbed its X host and regained the Wave Beam ability. With this ability, she was able to break into the Restricted Lab.

Inside the lab was a massive tube filled with several Infant Metroids floating about; in the next room, a mature Metroid, an Alpha Metroid, a Gamma Metroid, and a Zeta Metroid were being kept in large green tubes that resembled the Baby Metroid's container on Ceres Space Colony. While Samus was looking at these in shock, she realizes the Galactic Federation had lied to her about its intentions with the Metroids, which instead of extermination, they were researching and breeding these creatures.
Still looking about, the SA-X entered the Restricted Laboratory and released all the Infant Metroids in an attempt to destroy its natural enemy, firing on them with Super Missiles. Its plan backfired when the Metroids overwhelmed the SA-X, but the damage was done; the lab's security had been breached, and emergency fail-safes immediately took effect. A 1-minute countdown to the detachment of the entire Restricted Lab began; Samus was able to escape before the lab detached from the B.S.L. research station and self-destructed, killing the SA-X and what were apparently the last living Metroids in existence (though it is possible there are still Metroids being kept by either the Galactic Federation or Space Pirates somewhere). At least one Metroid escaped and quickly advanced to the Omega Metroid stage, where it was later killed by Samus when she was escaping the station.

Incidentally, the only actual Metroids in Metroid Fusion (aside from the escapee and Samus herself) are found in the Restricted Lab, and they do not actually damage Samus; they do fly around in a frenzy as Samus attempts to escape, and they can interfere with her attempts to Space Jump up the escape shaft. The most likely reason that the Metroids do not attack Samus is because they see her as one of them due to the Metroid DNA in her body (the Omega Metroid is an exception).

Trivia

• Parts of Fusion are inspired by the film Alien Resurrection; an example being the female protagonist being reborn as a hybrid of herself and both series' alien species. In Resurrection, Ellen Ripley, the protagonist of the Alien series, mourns when she kills her preceding seven clones by incinerating the lab, and at the end of the film when she flushes the Newborn out into the vacuum of space through a broken window pane. Unlike Ripley, Samus is never seen to have mourned the destruction of the Metroids in the Restricted Lab or her killing the Omega Metroid, even though she is considered to be a Metroid.
• The Restricted Laboratory contains a lot of similarities to the prequel's Sector Zero; Metroids were bred, station detaches via a fail-safe protocol if the area takes enough damage, both stations were detached by someone else rather than Samus, and both stations were successfully destroyed.
• It is possible that a Queen Metroid could have been bred as there was one prior to the prequel. However, it was also said they never expected one to grow to such lengths in a matter of time.