Nonotubes and nanowires are expected to have interesting thermophysical properties. For example, unusually high thermal conductivity and possibly low-temperature quantized thermal conductance have been predicted for carbon nanotubes (Berber et al. 2000). Meanwhile, other nanowires, such as Bi wires, may have suppressed thermal conductivity and high thermoelectric figure of merit (Volz and Chen). However, there lacks of experimental proof of these predictions because there are no established methods to measure the thermophysical properties of nanotubes and nanowires. Up to date, there are very few measurement data of thermal properties of nanotubes as well as nanowires (Hone et al. 1998, 1999, and 2000; Mizel et al., 1999). To provide a platform for concurrently measuring thermal conductivity and Seebeck coefficient of nanotubes and nanowires, a microdevice has been designed and used for measuring multiwall carbon nanotubes (MWCNs). Figure 1 shows the scanning electron micrographs of the microdevice. The device is a suspended structure consisting of two adjacent 10 μm × 10 μm silicon nitride (SiNx) membranes or islands suspended with three (or four) 200-μm long and 2 μm wide silicon nitride beams. One 30 nm thick, 200 nm wide, and 150 μm long platinum (Pt) heater/thermometer coil was built on each island. The heater coil is connected to contact pads with 200 μm long and 1μm wide Pt lines.