Colloidal interactions at fluid interfaces.

We discuss qualitative and quantitative aspects of the effective interactions between micrometer-sized colloids of different types trapped at fluid interfaces, with a particular emphasis on the relation between experimental and theoretical results. For colloids of that size, the interactions can broadly be classified into "direct" ones such as electrostatic, magnetic, or elastic ones. Such interactions appear also for colloids in bulk systems, but they are modified at interfaces. On the other hand, the presence of a fluid interface generates in addition interface-mediated (capillary) interactions which are either induced by nonspherical colloid shapes or by the "direct" interactions.