Doctor Darren Cross was the protégé of Hank Pym who usurped his mentor as CEO of Pym Technologies and rebranded it as Cross Technologies. His obsession with Pym's former creation of the Pym Particles caused him to try to replicate his own version, which he then intended to sell to HYDRA and the Ten Rings. Using his own version of Pym's Ant-Man Suit, he tried to fulfill the transaction, but he was challenged by Pym and Hope van Dyne, who destroyed his research with the assistance of Scott Lang. Driven mad by the failure, Cross wore the suit himself, becoming the Yellowjacket and tried to murder Lang and his family and eventually was shrunken down to a sub-atomic level after their battle.