  We discuss a simple model of particles hopping in one dimension with
attractive interactions. Taking a hydrodynamic limit in which the interaction
strength increases with the system size, we observe the formation of multiple
clusters of particles, each containing a finite fraction of the all the
particles in the system. These clusters are correlated in space, and the system
has a self-similar (fractal) structure. These results are related to
condensation phenomena in mass transport models and to a recent mathematical
analysis of the hydrodynamic limit in a related model.
