Suspensions of small particles in a fluid (‘aerosols’) are ubiquitous in the natural world and in technology. Such systems may be unstable due to collisions of the suspended particles, giving rise to aggregation or to chemical reaction(for example, collision processes are fundamental to understanding the growth ofraindroplets in clouds).

It is an empirical fact that turbulence has a significant effect on such collision processes (determining their rate as well as the outcome of a collsion: fragmentation or coalescence). I summarise recent theoretical resultsconcerning collision processes in turbulent aerosols.