Genos' Core

Overview
Core (コア, Koa): Genos' body is powered by an energy sphere labeled "CORE." It is attached to his body by a single cable and is held inside his chest. This is Genos' main source of energy, effectively his heart. If this core is destroyed or removed, Genos will die.

Near the end of Genos' fight against Mosquito Girl in attempt to self-destruct to take her out with him his core was seen filling up with energy and ready to explode. During his attempt to destroy the meteor, Genos removed the core from his chest and placed it in a similar holding place in his arm, in Arms Mode, to direct all the energy into his Incineration Cannon, making it more powerful. During his fight with Psykos and Orochi, it transpires that the core is a nuclear reactor.