Exciting research is being carried out in both external and internal gasdynamic phenomena at high Mach numbers. Dominantly experimental tools are employed to study the phenomena including high speed visualization and optical flow diagnostics such as PIV and PLIF. Several aspects of the unsteady non-linear nature of shock-shear layer interactions are being explored. Some of the interesting problems are supersonic mixing and its enhancement, complex nozzles, shock-mixing layer interactions, flow control in high speed flows, development of ground-based high speed aerodynamic test facilities.