For the novel, see Heart of TARDIS.

The Heart of the TARDIS was a core element of TARDIS technology, described by the Doctor as the ship's "soul." The connection to the Eye of Harmony was unclear. Whether it changed positions like other rooms in the TARDIS was unclear, but for the fifth, ninth, Tenth Doctor and eleventh Doctors, it was apparently located beneath the central console.

The heart worked to the keep the occupants

in time with their surroundings. If it suffered problems, such as a skipped beat, the TARDIS would materialise. (ST: 1963)

Commander Maxil removed the heart (or part of it) to stop the Doctor from leaving Gallifrey to prevent his execution. Damon reassembled and replaced it later to allow the Doctor to continue his travels. (DW: Arc of Infinity)

When trying to get Turlough to sabotage the TARDIS, the Black Guardian directed him to the heart of the TARDIS, describing it as a space-time element, ordering him to rip it out. While he could not remove it completely, he tampered with it enough to cause the TARDIS to begin to break up. It was this tampering that lead to Nyssa leaving the TARDIS. (DW: Terminus)

On one occasion, it opened as the TARDIS began to be ripped apart after Blon Slitheen had progra

mmed a Tribophysical waveform macro-kinetic extrapolator to tap into the greatest power source available, in this case the TARDIS. When Blon Slitheen looked into the Heart, she regressed to a Raxacoricofallapatorian egg, fulfilling her wish for a clean slate. (DW: Boom Town) On another occasion it was forcibly opened by Rose Tyler, Jackie Tyler and Mickey Smith, who used an attached chain and the pull of a large, yellow tow truck. (DW: The Parting of the Ways)

The Heart appeared to be bright energy which varied in colour from milky-white to orange. (DW: The Parting of the Ways) The Heart was also said to contain the last traces of Huon particles in the universe. Though this is because it was the Doctor's which was the last one in existence by this point. (DW: The Runaway Bride)

When Rose Tyler looked into the Heart, it fulfilled her wish to save the Doctor and infused her with god-like powers, so she could telepathically take the TARDIS to Satellite Five, where she saved the Doctor and destroyed a group of Daleks, including the Emperor. She was also infused with vortex energy. To save her life, the Ninth Doctor took the energy into himself

at the cost of his own life, regenerating into the Tenth Doctor. (DW: The Parting of the Ways)

After the Tenth Doctor's regeneration (DW: The End of Time) caused a massive deal of damage to the control room that forced a crash-landing, the console room was repaired and remodled into a new desgin. In this new look, the Heart was relocated to right below the console as opposed to being inside it, covered by a protective bubble. The cover also helped hold up the glass floor. (DW: The Eleventh Hour)

When the Silence took control of the TARDIS and caused it to explode in their hopes of killing the Doctor, the explosion seemed to start at the heart. (DW: The Pandorica Opens/The Big Bang)