The hexagonal form of boron nitride (h-BN) is analogous to graphite with a layered structure. BN nanotube is one of the most important non-carbon nanotubes. Compared to the carbon nanotube, BN nanotube shows an electrically insulator, having a high chemical stability, excellent mechanical properties, and a high thermal conductivity. In this review, we report novel synthesis of BN nanotubes and nanosheets for high purity and high yield growth. We will also introduce in-situ TEM observations on mechanical and electrical properties measurements from individual BN nanotube and nanosheet. The polymeric composites containing BN nanotubes will be demonstrated for improvement of the insulating high thermal conductivity.