- The AllSpark is an object in the Transformers: Prime continuity.
The AllSpark is the wellspring from which all life on Cybertron is born and ultimately returns. It resides in the Well of All Sparks. No surprise there. It is composed of pure energy and was contained within an indestructible container that was able to extract the AllSpark from the ether.
The container for the AllSpark was forged by Alpha Trion in order for Optimus Prime to launch it into space to keep it out of Megatron's hands. It was sent to the system of Theta Scorpii, which was one of the most hazardous star systems in the galaxy due to frequent gamma bursts and planetoid collisions, in order to deter Megatron from searching there.
Eons later, after Cybertron's Core had been restored by the use of cybermatter, Optimus Prime would leave the planet to find the AllSpark and bring it back to the Well of All Sparks so that new life could come to live on Cybertron. Because though with the core online again Cybertron could support life, without the AllSpark it could not create new life.
Optimus found the AllSpark and was able to return it to Cybertron. Unfortunately, Unicron (in possession of Megatron's body) was attempting to destroy Primus. Optimus, knowing that Unicron would destroy the AllSpark if given the chance, emptied the container into the Matrix of Leadership to protect it from Unicron. Though Optimus was successfully able to contain Unicron (in the same container that had once held the AllSpark) he had now literally become one with the AllSpark and so it was necessary for him to sacrifice himself in order to restore the AllSpark to the Well.
- Wheeljack's comment on the AllSpark's size is a reference to the Movie AllSpark which started out huge and was shrunk down to a much smaller size.