The physics of fluids confined in pores or slits can be strongly different from that observedin three spatial dimensions. In this talk I will present recent computer simulation and theoreticalresults on spatially confined colloidal systems. A well-known surface effect consistsof a layering of the particles which can be detected, e.g., by oscillations in the solvationforces. However, the length scales determining such forces are still under debate. Here Iwill discuss these issues for a film of charged colloids, including an interpretation via densityfunctional theory and a comparison with experimental (Colloidal-Probe AFM) data.Even more complex layering effects occur when the spatial confinement is supplementedby additional external fields. In particular, in films with dipolar interactions such as ferrofluids,external magnetic fields can give rise to layer formation, layer destruction, and fieldinducedcrystallization.