Aggregation and Crystallization in Space

Aggregation and crystal nucleation phenomena are among the subjects in condensed matter physics that still deserve a strong experimental effort to be fully grasped. This is in particular the case for macromolecular solutions or to dispersions of particles in the colloidal size range. Selfassembly, spontaneous ordering, structural organization on mesoscopic scales, are moreover key concepts for the design of nanostructured materials with specific functional properties. Although ground-based experiments performed on model systems have already shed light on many aspects of the latter phenomena, the presence of gravity often plays a noxious role. Density gradients induced by fast settling of large aggregates, or convective effects associated with the depletion zone around growing crystallites are just two well known examples. But gravity often yields additional and rather unexpected effects