Okay, I have a species of humanoids who are 1 micrometer tall, when fully grown. They have the same exterior proportions as humans, but due to their small size, they don’t need internal organs as we know it. They have these thin, bone-like crystals in their bodies that retains shape while allowing mobility, as well as organelles that do the tasks that their bodies need to do. Would such a species of unicellular humanoids be plausible?

Why or why not?

  • 3
    $\begingroup$ No, for many many reasons, from surface, area, to how muscles work, to how brains work. $\endgroup$
    – John
    Commented Apr 19, 2021 at 17:29
  • 4
    $\begingroup$ The bodies would need a very flexible interpretation of the word "humanoid", but something could be done. But brains? Nope. Not even close. The scale is several magnitudes down from possible. Also, of course, at that size neither hearing nor vision are at all feasible, the wavelengths are absurd compared to body size. Both light ans sound with short enough wavelength would be so energetic as to blast your poor being to shreds. $\endgroup$
    – PcMan
    Commented Apr 19, 2021 at 17:35
  • $\begingroup$ Endoskeleton for unicellular organisms would be problematic. $\endgroup$
    – Alexander
    Commented Apr 19, 2021 at 17:37
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    $\begingroup$ It depends on what you really mean by "humanoid". If you are OK with just shape (the way a ginseng root is "humanoid") something could be cobbled up. If you mean any kind of functional resemblance that's straight impossible. $\endgroup$
    – ZioByte
    Commented Apr 19, 2021 at 18:07
  • $\begingroup$ It possible to be smart about that problem, carefully throwing specs of handwavium for the problems mentiont in the comments(nice job guys, btw), but in general 1um is quite small volume, you can start count athoms at that scale, and definetly do so for molecules (if they are there) - handwave, it is funny concept, which can help represent microscale level with adventures and quantum effects aka magic, lol. But they will have rough live if their world is not polished enough... 0.5-1mm scale where something realistic can be $\endgroup$
    – MolbOrg
    Commented Apr 19, 2021 at 19:45

1 Answer 1


They already exist, if you throw in enough pareidolia.

Amoebas are pretty good at changing the shape of their unicellular body, and it can be happen that they might look, at a certain point, like a human shaped figure, like this photo demonstrates.

enter image description here

  • $\begingroup$ Nice.. a bit large though, the average Amoeba is 500-1000 times the requested size. $\endgroup$
    – PcMan
    Commented Apr 19, 2021 at 17:30
  • $\begingroup$ @PcMan It could be a small species of amoeba. $\endgroup$ Commented Apr 19, 2021 at 20:07

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