The Hulk has always been hard to kill, but that just got more difficult in the pages of Immortal Hulk.
Hulk finds himself in a precarious situation as he’s split up into parts and being studied by scientists of Shadow Base. After the scientist gets chewed out by his boss, he doesn’t seem happy about him. His anger is further incensed when Hulk’s head starts smiling at him. He tries to then intimidate Hulk by saying that the scientists will experiment on every part of his body and even cut his smile off. But Hulk just keeps on smiling.
Hulk’s hand kept in another jar begins to move, and before the scientist realised anything, Hulk began to snap his fingers, shattering all the jars in the lab. This sends all his body parts to the floor. The scientists ran away while Hulk’s body starting finding its way back together. He starts pleading Hulk to let him go away but Hulk’s body continued to merge around him, eventually taking him entirely, leaving only the shape of the hand reaching out to Hulk’s chest, before disappearing into Hulk entirely.
So it seems like the Hulk can survive being split apart, but his body can reassemble without any aid or medicine. He can also absorb matter into himself if the need arises.
Another noteworthy thing here is that Hulk could control his hand somehow mentally, as his hand was not connected to his body and was in a separate jar altogether. We’re sure he would find other ways to utilise these newfound abilities.
Here’s the official description of Immortal Hulk #8 by Al Ewing:
“Bruce Banner is dead. His corpse has been dissected, his organs catalogued, and his inner workings are being studied by the scientists of Shadow Base. Bruce Banner is no longer a threat. That just leaves the IMMORTAL HULK…”