Compression field

Compression fields were a type of technology used to fit large objects into small spaces.

Miniscopes used compression fields to keep specimens inside it miniaturised. Specimens extracted from the field resumed their original size. (DW: Carnival of Monsters)

Members of the Slitheen family used compression fields in their collars to allow them to wear human skins and disguise themselves. However, this had the side effect of frequent gas expulsion, and was limited to people of large sizes. (DW: Aliens of London, World War Three) By the 26th century, compression field technology had advanced to the point where they could fit inside the skins of thinner humans. (NSA: The Monsters Inside)

One of the Slitheen's compression fields was acquired by Henry van Statten and kept in the Vault. (DW: Dalek)