Fluids with nontrivial small-scale inhomogeneities (microstructure) include suspensions, emulsions, foams, polymer melts and solutions, surfactant solutions and liquid crystals. Flows of these complex fluids display features that are not found in simple fluids, including interfacial and bulk instabilities, texture formation and evolution and other novel flow phenomena that all can be traced back to the influence the fluid microstructure has on the stresses that develop within the flow. This workshop will focus on the experimental motivation and the constitutive modeling of complex fluids at all scales. Topics to be discussed include modeling from microscopic to mesoscopic to macroscopic, closures, constitutive model predictions including shear thinning and thickening regimes, inhomogeneities in flow including transient and steady state shearbanding, and shear induced phase transitions.