Exploration in microelectromechanical systems(MEMS) and nanotechnology requires evaluation techniques suitable for sub-micron length scale so that thermal and mechanical properties of novel materials can be investigated for optimal design of miro/nanostructures. The ultrafast optical pump-probe technique provides a contact-free and non-destructive way to characterize nanoscale thin-films, and its ultrahigh temporal resolution enables the study of heat-transport phenomena down to a sub-picosecond regime. This paper reviews the principle of optical pump-probe technique and introduces its application to the area of micro/nano-NDE.