This will parallel any thoughts in wonder about how atoms and molecules decide to come together and make a body.  How they can keep adding other atoms and molecules, and we call this phenom "growing", but at some point, they just decide to stop adding more.  So strange.  I have a big scar on the back of my right hand, and I laugh at how scars come to be.  It's as if the atoms and molecules are ticked off at you for interrupting their work, and they say "Screw you, we're not going to work there anymore."  and then there are some less bitter atoms and molecules that are like "oh, come on guys, we got to do something, we can't just leave a big gaping wound for him."  So then some others join in and say, "fine, but we're not going to make it look pretty, just cover the hole and then we're done."  And there it is.  Some slacker atoms and molecules didn't want to finish the job.  But then you have over achieving atoms and molecules of the chamaleon and gnute, they're like, "Hey, you just took away our tail!  We were using that!  F.  Now I'm going to have to start all over."