Interfacial surface generating means are disclosed which have an inlet end adapted to receive fluid, and outlet end adapted to discharge fluid, and a plurality of separate passage ways connecting the inlet end and outlet end, the passage ways opening (1) on the inlet end essentially along a first line lying approximately through the center of the inlet end and (2) on the outlet end essentially along a second line lying approximately through the center of the outlet end the second line being essentially normal to the first line. A plurality of the generating means can be used in series to make an interfacial surface generator which will produce many layers within a stream.