The Reverse Explosion

The Reverse Explosion was a subtype of the Explosion regeneration. The process began as a huge burst of regeneration energy, followed by the process slowing down and then allowing the change to take place in a quick judder. (PROSE: How to be a Time Lord)

An example of this was the Eleventh Doctor's regeneration, the first of a new regeneration cycle which had been granted to him by the Time Lords. Having been provided with additional regeneration energy, the elderly Eleventh Doctor used the explosion to destroy the Dalek ship, thus ending the Siege of Trenzalore. The Doctor then underwent a brief "reset" to his youthful appearance before returning to the TARDIS. (TV: The Time of the Doctor) After using the TARDIS telephone to send a call to Clara Oswald in the near future, convincing her to stay and help his next incarnation, (TV: Deep Breath) the Doctor met with the present Clara before changing into the Twelfth Doctor. (TV: The Time of the Doctor)