Emit each particle while scaling one after another How to emit each particle object, so that, say, each instance is scale = 0 when born, and scale = 1 when died? I remember we can do this in 2.49, but things seems being changed in 2.5+, in which the same action is being played simultaneously on all instances, instead of one after another.
Add a Texture under the Particle System:


Set it to gradient(Blend), set the mapping to Particle and influence Size:


This is what you get:


The rest is just setting the gradient and default particle size so when they die their size is 1. If they die at random then no, I think this cannot be done without some custom scripted particle generator with frame change handlers.