What three groups comprised the “parts” in heaven?

It’s difficult to draw this exactly out of what is written in the scriptures, but I would have reason to believe the three parts are the “noble and great ones”, the “not-so-nobles” and the “not-so-greats,” (to quote Brother Randy Bott, professor of religion, at Brigham Young University) and the part that was cast down (sons of Perdition).

I doubt our scriptures clearly outline the answer to this question, but there’s probably enough “reading between the lines” and commentary to draw some sort of conclusion. Of course, there’s an obvious answer: before the world was created. But I am wondering more specifically. There’s a lot of “eternity” behind the Creation.

Here’s a follow-up question you can consider.

Feel free to add your comments, citing scriptures/quotes or not.