Simulate expanding foam: How to spawn particles from other particles?


I need to create a expanding foam effect. You know, this thing:

It’s like this when you inject it

and then, in a few seconds, it expands 3x or 4x its volume and solidifies like this:

It’s for video render, no problem with FPS.

I have made an approach with morph targets prepared in Blender, and might be enough for this project, but I want to try Niagara for a more organic effect.

To do this I guess I need to spawn particles from other particles, but I don’t know how to do that with niagara. It’s easy in other particle systems I’ve used with 3DsMax or Nuke: At the end of the life of each particle, it spawns another one, or a bunch of them if you want an exponential growth.

I’m sure there must be an easy way to do that with Niagara, but can’t find any reference or example in the docs or in youtube tutorials.

Any cue?