Matter condensation

Matter condensation was a technique used to shrink inorganic or organic matter.

The Master picked up the technique "somewhere on his travels", according to the Fourth Doctor, and employed it with murderous outcomes, such as against a cameraman on Gallifrey. (TV: The Deadly Assassin)

It could be performed on humanoids, under the rays of a dimensional stabiliser from a TARDIS, without causing harm. (TV: The Invisible Enemy, The Armageddon Factor)