These are used by a Type 40 TARDIS when in Self-Repair Mode to "regenerate" and repair itself when damaged. This form of circuitry regeneration is one of the Time Lord's most advanced techniques. For their own safety, crew members should remain outside their TARDIS while it is self-repair mode. For this reason the Control Room is deprived of oxygen during self-repair. Given time a TARDIS can rebuild/grow new Control Rooms (if one is destroyed or jettisoned). However, the Molecular Stabilizers cannot manufacture raw elements such as Mercury or Zyton-7. TARDIS scar tissue bears a strong resemblance to mercury.