  Fluctuations of the interface between coexisting colloidal fluid phases have
been measured with confocal microscopy. Due to a very low surface tension, the
thermal motions of the interface are so slow, that a record can be made of the
positions of the interface. The theory of the interfacial height fluctuations
is developed. For a host of correlation functions, the experimental data are
compared with the theoretical expressions. The agreement between theory and
experiment is remarkably good.
