xpMorph General tab menu.
Checking this box activates xpMorph.
Set at Independent, by default.
You can change this to Action-Controlled.
In this mode, particles will be affected if they come into the field of effect of the modifier.
When in the Action-Controlled Mode setting, the modifier will only act on a particle when told to do so by an action.
Set as Change Value Over Time.
The alternative setting is Set Value.