What makes it impossible to have identical fingerprints?

Question: What makes it impossible to have identical fingerprints?
- Keywords:
  body,
  fingerprint
Asked by lisaloo to Claire, Kate, Matt, Rob, Sam on 21 Jun 2013.
- Claire Lee answered on 21 Jun 2013:
  
  Your fingerprints are formed partly due to the movement of the amniotic fluid around you when you were a baby in your mum’s tummy. This is why even identical twins have different fingerprints, because the movement of the fluid around each of their hands will be different
- Sam Geen answered on 21 Jun 2013:
  
  There are so many possibilities for fingerprints that it’s not impossible that two people would have identical fingerprints – it’s just very very unlikely!

Question: What makes it impossible to have identical fingerprints?