Transdimensional engineering
Transcendental engineering is the technology of creating dimensionally transcendental objects which The Doctor proclaimed this a "key Time Lord discovery". (DW: The Robots of Death) It enabled TARDISes to exist.
Other than the Time Lords, the Daleks (DW: The Chase, The Evil of the Daleks) and Mawdryn's people, who sought to emulate the Time Lords, had developed this technology and employed it in their transmat capsules. Odly in Doomsday the cult of Skaro refer to this as "Time Lord Technoloy" which suggest that they too, emulated them.
A young Trion officer seemed unfazed by the dimensionally transcendental interior of the Doctor's TARDIS which suggests his species had some familiarity with this kind of science. (DW: Planet of Fire)
The War Lords possessed dimensionally transcendental space-time vessels known as SIDRATs, though only through the intervention of a renegade Time Lord, the War Chief. (DW: The War Games)
