Viewed from the perspective of larger things, the holon is a part. Viewed as an entity in its own right, it is a whole that has parts. And at its own level, it has some "reality" of its own. From this viewpoint, everything is a holon. So a holon isn't a special thing, per se, but a thing (any thing) seen from a holistic perspective.
When you consider reality as made up of holons, it can be viewed as a hierarchy of small things making up larger things -- atoms, molecules, cells, organisms, and so on. But that hierarchy is in no way as linear as it first looks; things may be more complex than that. For example, you (a human being) can be divided into cells, and into facets of your personality, and into various organic processes, and .... Likewise, you are part of a community, and part of the gravitational mass of Earth, and part of the readership of Wikipedia, and ....
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