Convective instabilities in complex systems with partly free surface

Experiments and observations and some selected theoretical studies of thermocapillary instabilities are reviewed and presented together with new unpublished work. We start with simple idealized model systems of pure thermocapillarity and add to them more complex features like gravity forces, temperature gradients inclined to the free surface, static and dynamic surface deformations, solutocapillary effects and reacting or moving crystal boundaries (like during unidirectional solidification). Many effects and instabilities are demonstrated in video clips which can be downloaded from http://meyweb.physik.uni-giessen.de/1_Forschung/crystalgrowth/video/homepage.html. We try to point out the relationship of thermocapillary instabilities in the more complex systems with those in theoretical studies where the names of these instabilities have been coined.