Narcomoeba's ability while resolving a draw spell

[Mojeh]

Let's say I resolved a Breakthrough and on it's second draw I dredged a Golgari Grave-Troll and a Narcomoeba hits the graveyard. My question is: does the ability of Narcomoeba resolves as I finish the current dredge, or it waits until the last Breakthrough's draw?

[ScatmanX]

Let's say I resolved a Breakthrough and on it's second draw I dredged a Golgari Grave-Troll and a Narcomoeba hits the graveyard. My question is: does the ability of Narcomoeba resolves as I finish the current dredge, or it waits until the last Breakthrough's draw?
Narcomoeba's ability goes to the stack, but can only resolve when you get priority, and that can never happen in the middle of the resolution of a spell. So it will only go to the battlefield after you draw (or dredge) and then discard all the cards to Breaktrough.

[Mojeh]

So the ability goes to the stack during the resolution of Breakthrough, but only resolves after it's done. I've made a confusion because I once thought the Narcomoeba's ability was some kind of change effect, not a triggered ability.
Thanks for the answer.

[Ryoku]

Just to make a minor clarification:

If abilities would trigger during the resolution of the spell or ability, the trigger is declared, but they are not put on the stack until the spell or ability resolves. This is slightly different than what ScatmanX said, since you can choose the order of the triggers that you put on the stack if multiple triggers happen.

[Infinitium]

In addition, Narcomoeba will stay in its current zone (ie the graveyard) until its ability is done resolving, hence why well timed gravehate tend to screw it over.