Thin walled, carbon tubular structures (see Figure and also cover) with varying inner diameters. in the form of nozzles, straight tubes, tube-on-cones, and funnels have been synthesized by in-situ control of gallium-carbon wetting behavior using gas phase chemistry. In addition, carbon tubular structures with large internal diameters have been coalesced during growth to create Y-junctions suitable for micro/nano-fluidic applications.