Let me start with an obligatory reference to one of the great worldbuilders of Science Fiction: Hal Clement. In Needle the alien visitor was a hard-SF take on the classic "blob". It was explained that rather than being descendant from life using cells, it came from viruses, or something like that.
Note that researches work with "cell free" cultures, which is basically the gunk from inside a large number of cells but without walls cutting it up into little compartments.
Some "compartments" in nature are not microscopic. Look at algae in particular.
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