This chapter describes binary polymer mixtures with the dynamical symmetry described in Sect. 2.2 under external flow fields. The flow fields break the macroscopically phase-separated two-phaseMacroscopically phase-separated two-phase structure and self-organizes a series of characteristic dissipative structures as classified from Regime I to IV under increased flow rate, including flow-inducedCluster-to-percolation transition cluster-to-percolation transitionFlow-induced cluster-to-percolation transition in Regime III and stable stringsStrings aligned along flow direction in Regime IV. The flow eventually brings about the liquid–liquid phase transition (“bifurcation”) from the two-phase (in Regime IV) to single-phase mixture (in Regime V). This chapter presents self-organization of order/disorder through evolution of a series of the dissipative structures. Specifically the following themes are discussed: Flow-induced phase transition from two-phase to single-phase with increased shear rateShear rate: Shear-induced shift of phase transition temperature: Time evolution of dissipative structures at the strong shear regime after shear drop from shear-induced single- phase state: Scaling law in the critical phenomena on space–time self-organization of dissipative structuresSpace–time self-organization of dissipative structures under flow: Reversible changes of the steady-state structures with shear rateShear rate. This chapter also describes off-critical mixturesOff-critical mixtures under flow as follows: Composition dependence of dissipative structures and flow-induced phase transition: Uniformity of droplet size in Regime II: Flow-induced phase transition in off-critical mixtures: Hysteresis in phase transition of off-critical mixtures: Shear-rate dependent “steady-state phase diagram” or “phase diagram at dynamic equilibrium”.