Separated flow is a very common type of flow occurring not only in engineering, but also in biological circumstances. Since the flow separation has direct effects on the performance of natural or man-made flow systems, such as lift, drag and noise, it is essential to control separated flows in a desired way. In this talk, first, some mechanisms of separation control will be discussed with examples of biological and bluff-body flows. The key strategy of separation control is to enhance the near-wall momentum in order to delay the main separation. The enhancement of near-wall momentum can be achieved through the boundary-layer transition to turbulence or through the generation of streamwise vortex. Second, recent examples of application of separation control will be introduced. Examples include a new golf ball that does not have dimples but grooves for drag reduction and biomimetic axial fan that has protrusions at the leading edge for noise reduction. Finally, prospective research issues will be suggested in developing practical and effective methods of controlling separated flows.