Explode then come back together

I’m having a bit of trouble with one of my projects… I want an object to explode from one form, and then come back together to form into another shape. I have the shape keys down, and I have everything where i want it, but i can’t figure out how to put it back together after its exploded. if anyone could send a link to a tutorial, or if you can describe in detail how to do it, it would be much appreciated.