Subspace compression anomaly
A subspace compression anomaly was a rare subspace astronomical phenomenon that miniaturized objects that entered its accretion disk. These anomalies emitted a flux of gamma radiation.

In 2374, Starfleet ordered the  to investigate one such anomaly, in the hopes of collecting data that could lead to the development of transwarp corridors. The runabout  was lowered into the anomaly with a tractor beam, where it shrank to a fraction of its normal size. 

The mission was interrupted by a Jem'Hadar ambush. Contrary to predictions, the Rubicon did not return to normal size when it left the anomaly. After helping to defeat the Jem'Hadar in its miniaturized state, the runabout and its crew were restored to normal size by re-entering the anomaly along its previous course. ()

See also 
 Subspace compression

External link
 

de:Subraumkompressionsphänomen
nl:Subruimte compressie
compression anomaly