Doctor Darren Cross was the protégé of Hank Pym who usurped his mentor as CEO of Pym Technologies and rebranded it as Cross Technologies. Cross became obssessed with the Pym Particles and using Pym's technologies to achieve success, but the constant exposure to the particles negatively affected his mind. Cross had developed the Yellowjacket Suit and intended to sell it to HYDRA and the Ten Rings but Pym and Hope van Dyne joined forces with Ant-Man who destroyed his entire research. Driven mad after losing everything he built, Cross wore the suit himself and became Yellowjacket, to get revenge by killing Ant-Man and his family. As Cross threatened Cassie Lang, he was confronted by Ant-Man, who neutralized him by shrinking him down to a sub-atomic level. Now trapped in the Quantum Realm, Cross' mutilated form was found by Kang the Conqueror, who provided him with a mechanical form. Dubbed as the Mechanized Organism Designed Only for Killing, or M.O.D.O.K., Cross spent ten years serving Kang.