This photo shows the development of a flow instability in an axisymmetric jet. On the left, the jet is smooth and fully laminar, but, by the center of the photo, disturbances in the jet have grown large enough to distort the laminar profile. The jet is then in transition; by the right side of the frame, it has reached a turbulent state, as evidenced by the increased mixing (which causes the smoke to disperse more quickly) and intermittency of the flow. #