How do Catapillars turn into Butterflys and how ?

Question: How do Catapillars turn into Butterflys and how ?
- Keywords:
  animal,
  butterfly,
  caterpillar,
  development
Asked by mattc003 to Darren on 19 Mar 2012.
- Darren Logan answered on 19 Mar 2012:
  
  They go through a process called metamorphosis.
  
  It basically involved building a barrier to protect themselves (a cocoon) and then they express a lot of new genes which cause their bodies to reashape and grow into a different form. It seems miraculous, but its only really a very extreme version of what happens to use as we change from children to adults. We also express lots of new genes, we change physically and emerge from puberty really quite different than how we entered it!

Question: How do Catapillars turn into Butterflys and how ?