[sonic45132]

They take your existing hair follicles from areas that aren't thinning and move them to the thinning or bald area.

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So in theory if I want less head-hair and more chest-hair, I could in theory do this by moving the hair follicles? Interesting stuff.

[Tangurena2]

That would not be practical. Visible body hair (and head hair) is "terminal hair". Peach fuzz is "vellus hair". Androgens turn vellus hair into terminal hairs (and are also the driving force for male pattern baldness). There was a big stink on social media about the character Aloy in the game Horizon who had vellus hairs visible on her face - like every other human woman.

https://en.wikipedia.org/wiki/Terminal_hair