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Correct me if i am wrong, if we cut 2mm from eyebrow hair, it will grow 2mm and then stop growing, or if we cut 5mm, then it will grow only 5mm. My question is, does hair know how long to grow ?

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marked as duplicate by WYSIWYG Jan 18 '16 at 5:55

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    $\begingroup$ Probably easier to understand if you look at the answer for a dogs coat. en.wikipedia.org/wiki/… Short answer is it is controlled by gene expression. $\endgroup$ – AMR Jan 12 '16 at 0:40
  • $\begingroup$ Individual hairs fall out after they grow for a certain amount of time. If you cut off 2mm of hair, those hairs will grow to what would be their maximum length (had you not cut them), then fall out and are replaced by uncut hairs that grow to maximum length. $\endgroup$ – C_Z_ Jan 12 '16 at 17:23

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