The Growing Man is an android build by an extra-dimensional race on behalf of the time-travelling villain known as Kang the Conqueror, who had subjugated their planet, Kosmos. Knowing that the android would be used as a weapon in the past, the scientists of Kosmos built a device into the android which would deliver a warning message to their people and hopefully lead their ancestors to prepare for Kang's coming. However, the device somehow became damaged, as Kang used the Growing Man many times without the alert beacon functioning.
In the Growing Man's first recorded appearance on Earth, it battled the Asgardian god Thor on Earth. Thor rid himself of both the Growing Man and Kang by entrapping them in a dimensional warp created by his enchanted hammer.
Months later, Kang used the Growing Man to abduct millionaire inventor Tony Stark (secretly the hero Iron Man) from a hospital after Stark had suffered a heart attack. Iron Man's teammates in The Avengers attacked and followed the Growing Man, as Kang had intended, enabling him to transport them to his own future time period, where he involved them in his competition against the alien Grandmaster.
Still later, members of the alien Colonizers of Rigel removed the Growing Man from Kang's time ship, which had apparently been abandoned in the 20th century following one of Kang's defeats. The Rigellians sent the Growing Man to Earth, where it battled Iron Man, who defeated it by using electrical cables to drain its power, rendering it inert.
Kang revived the Growing Man and sent it into New York City during a demonic invasion. In order to maintain his continued existence, Kang believed he had to insure the Avengers, whose ranks were then depleted, would be reborn. Therefore, his Growing Man constantly fought to bring the heroes Captain America (then "The Captain"), Thor, Gilgamesh, Mr. Fantastic, and the Invisible Woman into conflict as the Avengers. Mister Fantastic, who had recently joined the team temporarily, used his scientific talents to devise a means of reversing the process that enables the Growing Man to enlarge its size. As a result, the Growing Man shrank to such a degree that it vanished from sight.
The Growing Man was later recovered by the subversive organization HYDRA, led by terrorist Baron Strucker. Strucker ordered the Growing Man to be let loose in New York as part of a ploy to destroy the formative team called the Thunderbolts, who were attempting to fill the shoes of the missing Avengers following in the wake of the Onslaught incident. The Thunderbolts managed to not only defeat the android, but to activate its warning beacon, which depleted the Growing Man's energy reserves, returning it to dormancy. The Kosmosian aliens later traced the beacon to the Thunderbolts, in hopes to learn more of Earth and the future, and kidnapped the team to Kosmos, embroiling them into their civil war.