Clusters of Particles in a Vibrating Fluid
"Ordered clusters and dynamical states of particles in a vibrated fluid," Greg A. Voth, B. Bigger, M.R. Buckley, W. Losert , M.P. Brenner, H.A. Stone, and J.P. Gollub, Preprint, (pdf format, 0.5Mb)
Fluid-mediated interactions between particles in a vibrating fluid lead to both long range attraction and short range repulsion. The resulting patterns include hexagonally ordered micro-crystallites, time-periodic structures, and chaotic fluctuating patterns with complex dynamics. A model based on streaming flow gives a reasonable account of the attractive part of the interaction.
Look here for Animations of several of the intriguing
states that form.