A quantum stasis field prevented a Changeling from altering its biomolecular structure. A prototype of a device that could emit such a stasis field was developed by the Obsidian Order and tested by Elim Garak in 2371 during his interrogation of Odo aboard a Romulan warbird. The technology proved to be highly effective in forcing Odo to stay in his humanoid form, preventing him from either changing shape or from entering his liquid form to regenerate. As a result, Odo began to lose molecular cohesion with considerable agony until Garak finally deactivated the device and allowed the Changeling to enter his dormant state. (DS9: "The Die is Cast")
In the DS9 anniversary trilogy Star Trek: Deep Space Nine - Millennium, when trapped in the future, Odo encounters a version of Weyoun whose loyalties have shifted from the Changelings to the Prophets, who briefly traps Odo using another quantum stasis field generator, although he retains enough respect for Odo to release him.