A highly important part of Transformer biology. It is the organ that is responsible for their namesake ability.
A mass of Bio-Circuits and and energy path ways, the Tranformation Cog is almost like a second brain, but it is devoted only the lower brain functions (the body), controling and driving the transformation process. A bot's second form is 'remembered' by the cog and it is what starts the transformation process.
In the process, the bot's body begins a metamorphosis, parts of the body may be even liquefied and restructured to become the alternate form. Organs may be shifted into their alternate mode's counterparts. The head is collapsed in and integrated into the new form. The only thing that remains untouched is, like reconstructive armor, the Spinal column, which is composed of the spine, the Spark Chamber and the Brain Module.
Generally, the body twists and turns as limbs contract and the exo-armor restructures its self to become the alternate mode with the protoform hidden inside.
Interestingly, this transformation is often not seen as the insides morphing, but the bot 'unfolding' out of its alternate mode.
A Transformation Cog can generally only hold one Alternate Mode.