Abstract: An interfacial surface generator for mixing fluids is disclosed that has a plurality of mixing elements positioned in a tubular housing in end-to-end relationship. Each element has a cavity on its upstream end and a protuberance on the downstream end. The protuberance on each element extends into the cavity of the adjacent element to form a narrow annular passageway between the side of the protuberance and the wall of the cavity and a narrow space between the end of the protuberance and the bottom of the cavity. Each element also has a central blind-end passageway that connects the space between the end of the protuberance and the bottom of the cavity with a plurality of radially extending passageways that connect the central passageway to the annular space between the protuberance and the wall of the cavity. The fluids being mixed flow together through the central passageway.