xpHistory provides a localised, non-saveable cache, which you can use to play back the animation of a particle.

General tab

The xpHistory General tab.

Enabled

Checking this box enables the xpHistory modifier.

xpHistory_Disabled.mp4

Enabled is unticked, in this animation.

xpHistory_Enabled.mp4

With Enabled checked, the repeat occurs at the At Time setting of frame 75.

Mode

Set at Independent, by default.

You can change this to Action-Controlled.

Independent Mode

In this mode, particles will be affected if they come into the field of effect of the modifier.

Action-Controlled Mode

When in the Action-Controlled setting, the modifier will only act on a particle when told to do so by an action.

Until that point, the particle will not be affected, but once activated for a particular particle, the modifier will influence the particle - that is, it will play back the history.

At Time

This is the time in the document when playback will start.