A molecular reversion field was a spatial anomaly that could interfere with transporter patterns and the molecular structures of objects passing through it. A shuttle from the Enterprise-D encountered one in 2369, where a transport beam through the phenomenon "de-aged" the occupants who were on board. (TNG: "Rascals")
History[]
Star Trek: Phoenix-X[]
In 2383, the USS Phoenix-X transported Kayl, a woman so aged, she was close to death, off of an alien ship trapped in a molecular reversion field. The transport "de-aged" her into a healthy, young, adult. Lieutenant Commander Kugo speculated that the power of the transporters, which were much stronger on most Starfleet vessels by this year-- as compared to the Enterprise-D's, 15 years earlier-- may have prevented Kayl from becoming a child. The Phoenix-X also became trapped within this field. But after repolarizing the hull to deflect the field, the ship was released. ("Life 2")
In 2404, Night Seifer led several crews and their starships, including Captains Reynolds, Menrow, Iviok and Aeris to be caught in a massive molecular reversion field, intermixed with an ion storm, in the Tilonian system, the result of which caused everyone involved to undergo a reduction in age. The trauma from the accident caused all included to temporarily lose years of memories and retake Starfleet Academy. ("Delta Recruit", "Kobayashi Maru", "Celestial Dynamics")
External link[]
Molecular reversion field article at Memory Alpha, the canon Star Trek wiki.