Miniaturisation

Miniaturisation was a techonology used to shrink inorganic or organic matter, usually with compression field or moleculon nanoscaler technology.

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)

In 1964, England, the First Doctor and his companions Susan, Ian and Barbara experienced a miniaturisation, solved by the TARDIS. (TV: Planet of Giants) The Doctor, Ian and Barbara were miniaturised again on a later visit. (COMIC: Dr Who in "Lilliput")

In 1966, the faceless Chameleons miniaturised and stored young Earthlings from all over Europe; their purpose was to steal their identities, lost after a catastrophe on their planet. Planes were used as miniaturisation chambers. (TV: The Faceless Ones)

During the 57th Segment of Time, on the Ark, most of the Earth population, fleeing from their home, had been miniaturised and placed in suspended animation in order to face a 700 years journey towards Refusis II. A Minifier was the instrument geared for this purpose. Miniaturisation was administered as a sanction too. (TV: The Ark)

The Fourth Doctor and Adric encountered a Genesis III supercomputer that was miniaturising people so that they could live on a single atom, thus cutting their carbon emissions. A side effect of this was that time on the atom passed far more quickly. (COMIC: Inter-Galactic Cat)

Visitors to Little Green Storage were shrunk to 7.5% of their original size. (PROSE: Borrowed Time)

The Teselecta used a miniaturisation ray to shrink people, and a compression field to keep its crew shrunk. (TV: Let's Kill Hitler)

The crew of the Aristotle used a moleculon nanoscaler to shrink the Twelfth Doctor, Clara Oswald, Journey Blue, Gretchen Carlisle and Ross to enter inside "Rusty", a malfunctioning Dalek. (TV: Into the Dalek)

In a hospital in Holby Space City, a Professor cloned himself,, and PAND-R, then shrunk themselves and went on a "Fantastic Journey" inside Iris to cure her of a lurgy she likely caught from a sandwich from a dodgy motorway services while travelling in the solar system in the 30th century. The lurgy turned out to be a giant prawn. (PROSE: From Wildthyme with Love)

In an introduction that wrote for Doctor Who Magazine, he admitted that his life as the megalomaniac's megalomaniac wasn't all "murder, miniaturisation, and mercenary acts", and did have acts of so-called "charity work", which often involved more murder. (PROSE: A letter from the Master)

Similar technologies
The Master employed the technique of matter condensation with fatal outcomes, through the use of their Tissue Compression Eliminator. (TV: Terror of the Autons, The Deadly Assassin et al.) On one occasion, the TCE accidentally shrank the Master himself, without killing him; the effect was neutralised by exposure to Numismaton Gas. (TV: Planet of Fire)