Hi Ann there's 3 ways depending on the type of effect you want. The "visibility" property allows you to fade out and fade in the emitter whenever you want it to. The "active" property (active/inactive) causes the emitter to disappear completely when you make it inactive, and it starts emitting from the beginning again when you make it active again. The "number" property allows you to animate the rate of particle emission, so you can make it zero when you want the emitter to disappear, but it does not disappear immediately like in the "active" property: the remaining particles which have already begun their life continue until their life is done, in this case. You would use whichever of the 3 ways gives you the effect you want at the time.