This question already has an answer here:
There are a number of cards that have two different actions. Ponder is one of them. I assume these separate actions are in sequence, and cannot be responded to by placing items on the stack in between the steps. But, I can't confirm that in the rules.
Game situation in which this came up (in case this helps explain why one would want to do this.)
I have a Lion Eye Diamond on the table, and I cast Ponder. Ponder resolves, I draw my three cards, and put them back on top of the deck. The top of the library is now a game winner if I can get 3 more mana. [Say it's Coalition Victory but I only have RWGUB available and meet all other requirements] So, would like to fire off the Lion's Eye Diamond before I perform the second step of Ponder and draw that card.
Note: Lion's Eye Diamond can only be activated at instant speed (see the link) even though in all other ways it is a mana source.
Can I win this game this turn? [assuming no counter spells of course...]