This is a very common effect yet a bit difficult to create. Basically is by using "memory" operator to memorize object's initial position, and then use "BringTo" to reconstruct it.
3. Memorize their (debris) initial position.
3. Randomize their position.
4. This step is the most important step. We keyframe "Aligment" and "Scale", whatever particle entering activate state, after 100 frame (controls by timer), particle will scale up from 0% to 100% (between frame 0 to 5) , from 270 degree of X rotation to 0 degree (between frame 0 to 5).
5. Now we need to bring particle to it's original position. We retrieved position data from Step 3. And that's it. Hope you enjoy my tutorial!