Subject: What exactly happens during metamorphisis of a butterfly?

This has been a major topic of discussion in my science class.  For
 so long, teachers have been bringing caterpillars in their classrooms 
for students to observe metamorphosis but they don't really talk
 about what really goes on inside.  I talked to a third grader who
thought caterpillars ate something light and magic then woke up and saw
their wings.  Cute, but I couldn't tell her what really happened and even 
my college science teacher could not tell me.  I have looked all over 
the place and I have not found an answer that is solid.  So, I am hoping
 you can help me out.  Thank you for your time.

Re: What exactly happens during metamorphisis of a butterfly?