A sheath flow system having a channel with at least one fluid transporting structure located in the top and bottom surfaces situated so as to transport the sheath fluid laterally across the channel to provide sheath fluid fully surrounding the core solution. At the point of introduction into the channel, the sheath fluid and core solutions flow side by side within the channel or the core solution may be bounded on either side by the sheath fluid. The system is functional over a broad channel size range and with liquids of high or low viscosity. A wide variety of shapes of fibers and other materials can be produced from this system through the use of polymerizable material.