what are some interesting facts you know about the skin?

Question: what are some interesting facts you know about the skin?
- Keywords:
  body,
  human. body,
  skin
Asked by alishawatt1 to Janet on 13 Mar 2013.
- Janet Daly answered on 13 Mar 2013:
  
  It’s the biggest organ in the body, it completely replaces itself every 21 days, it makes vitamin D (with the help of sunlight)…

Question: what are some interesting facts you know about the skin?