^ That makes so much sense.
If I recall correctly, the Thing's true form is visible to the naked human eye in the novel Who Goes There?, but the movies are only based on the novel; they don't necessarily follow all the same rules.
In a deleted scene from the 1982 movie, Blair says that he doesn't think the alien has any kind of cell structure, at least not as we know cell structure.
Virtually everyone assumes that the Thing Beasts/Imitations fundamentally comprise of The Thing's mere cells, but perhaps what we assumed to be its cells are actually the creature itself; or creatures themselves, rather. That would explain why every piece can operate independently of all others.
So this is my theory: The Thing is a microscopic organism that can fuse with others of its kind to increase its size, intelligence and physical capabilities. Its digestive and reproductive processes are one and the same; when it absorbs organic material (e.g., animal cells), it somehow turns it into a member of its own kind gives them the fuel they need to asexually reproduce. The more lifeforms it absorbs, the larger its collective mass grows, and larger masses can absorb larger lifeforms at a faster rate. While The Things prefer to remain united, they will break off pieces of themselves whenever it is most conducive to their survival and reproduction. They will also take on any form they can in order to meet these ends; that includes imitating its prey/enemies whenever necessary.
On an individual level, it's just an animal with no other purpose than to survive and reproduce, but who knows how its motives may evolve as it absorbs more and more intelligent lifeforms? The original backstory of the 2011 prequel is that The Thing was a mere specimen on the ship it crashed here in, but I've always assumed it was the pilot. At some point, it grew sophisticated enough to build a spacecraft that enabled it to explore the cosmos for who-knows-how-long, but something went wrong as it entered our atmosphere.
Maybe the mass that crashed here is only a small fragment of its entire species; a piece that was broken off and sent away to seek more worlds, more knowledge and more power. But as Peter Watts suggested in 'The Things' (an award-winning short story written from the Thing's perspective), the pilot's body was scattered in the crash, causing it to lose most of its memories, reducing it to more primitive forms, and forcing it to restart its mission from scratch.
