The presence of organized motions and structures in turbulent shear flows was apparent for a long time, and has been additionally implied by mixing length hypothesis even before the concept was explicitly stated in literature. There were also early correlation data found by measuring jets and turbulent wakes, particularly by Corrsin and Roshko. Hama's hydrogen bubble technique, which used flow visualization to observe the structures, received wide spread attention and many researchers followed up including Kline. Flow visualization is a laboratory experimental technique that is used to visualize and understand the structures of turbulent shear flows. With a much better understanding of coherent structures, it is now possible to discover and recognize many coherent structures in previous flow-visualization pictures collected of various turbulent flows taken decades ago. Computer simulations are now being the dominant tool for understanding and visualizing coherent flow structures. The ability to compute the necessary time-dependent Navier–Stokes equations produces graphic presentations at a much more sophisticated level, and can additionally be visualized at different planes and resolutions, exceeding the expected sizes and speeds previously generated in laboratory experiments. However, controlled flow visualization experiments are still necessary to direct, develop, and validate the numerical simulations now dominant in the field.