Grimm's college roommate was Reed Richards, a brilliant science student who became his closest friend.  During their first meeting, Richards confided in Grimm his intention to someday build a starship for interstellar travel.  Grimm jokingly promised that he would pilot the starship for Richards should he ever build it.

Upon graduating, Grimm went into the U.S. Air Force and became a highly skilled test pilot and astronaut.  In the mean time, Richards went ahead with his project to build a starship, using both his own fortune and funding from the U.S. government.  When the federal government threatened to withdraw its funding from the starship project, Reed Richards decided to take the starship on a test flight himself as soon as possible.  Grimm was persuaded to serve as pilot, and Richards' future wife Susan Storm, and her young brother Johnny insisted on going as passengers.  The four were subject to intense cosmic ray bombardment.  The controls, too, were damaged, and pilot Grimm was forced to abort the flight and return to Earth.

The four young people discovered that the cosmic radiation had triggered mutagenic changes in their bodies.  Grimm was transformed into an orange-colored, thick-skinned, heavily muscled, and superhumanly strong "thing."  Grimm, morose over his new grotesque appearance, named himself the Thing,  Under Richards' leadership, the Fantastic Four has become Earth's most honored team of superhuman adventurers.

Over the years, the Thing's epidermis has changed from an abnormally dense, somewhat lumpy, but still comparatively smooth hide through a long-term stage as a flexible, interlocking network of rocklike lumps, to its recent form as a network of rough, spiky plates.  His superhuman strength has increased considerably with each change.

Early in Grimm's life as the Thing, he would sometimes revert to his original human form unexpectedly.  But neither the changes nor Richards efforts to turn Grimm back to human form have ever proven to be permanent.  Instrumental in helping Grimm to adjust to his life as the Thing was the blind sculptress Alicia Masters, with whom Grimm fell in love.  Grimm achieved the ability to transform from his Thing form to human form and back at will.  However, fearing that Alicia Masters could love him only as the Thing, Grimm suffered from a subconscious block that prevented him from being human.

When Grimm was transported to the distant "Battleworld" by the alien Beyonder for the first of the so-called "secret wars," he found himself able to change to human form and back.

Once the secret war was over, Grimm remained on the planet for months.  Eventually, however, he found himself trapped once again in his monstrous form, and he returned to Earth.  There Grimm learned that Johnny Storm and Alicia Masters had become lovers, and that Reed Richards had known about his mental block.  Grimm became furious and distraught and quit the Fantastic Four, following which he worked for a time as a superhumanly strong wrestler for the Unlimited Class Wrestling Federation, and also participated in missions with the West Coast Avengers.

When Reed and Sue Richards announced they were leaving the Fantastic Four to rear their son in relative normality, the Thing became head of the group.  He has shown himself to be an able, level-headed leader.  However, he still harbored some resentment toward the Human Torch due to Johnny's marriage to Alicia.  Still, the addition of Ms. Marvel II to the Fantastic Four gave Ben a realistic outlet for his long-submerged romantic side.  When Ms. Marvel initially joined the Fantastic Four, Ben was concerned with helping her develop a stable, healthy outlook on life.  Since the accident that transformed her into a "she-thing" and him into his more powerful spiked form, they saw each other as ideal mates.