Laminar-to-turbulent transition is of great practical interest as it occurs in many engineering flows and often plays a critical role in aerodynamics and heat transfer performance of those flow devices. There could be many routes through transition, depending on flow configuration, geometry and the way in which transition is initiated by a wide range of possible background disturbances such as free-stream turbulence, pressure gradient, acoustic noise, wall roughness and obstructions, periodic unsteady disturbance and so on. This paper presents a brief overview of transition in general and focuses more on the transition process in the free shear layer of separated-reattached flows, demonstrating that above certain free-stream turbulence intensity a so called bypass transition could occurN/
