“Rheology without morphology...,” as the saying goes, becomes more unsatisfactory as complex fluids with increasingly complex rheological behavior are investigated. However, developing structure-property relationships for flowing colloidal dispersions, self-assembled surfactant solutions, polymer solutions and other complex fluids requires measurements of the microstructure under flow. Small angle scattering, and in particular, neutron scattering with the advantages of contrast matching techniques, provides one of the most complete methods for interrogating microstructure on the submicron length scale. The most relevant microstructure for a system in simple shear is in the flow-flow gradient plane (1-2 plane), which is the hardest to access in a scattering experiment. To address this need for direct measurements under flow, we have developed instruments for flow-SANS in the 1-2 plane based on a short-gap Couette cell. Further, as some systems can exhibit flow instabilities, such as shear banding, we have collimated the beam into slits as thin as 100 microns to enable exploring structure in different regions of the flow field. The instrument, its calibration, and examples of results are presented. Case studies include a shear thinning and shear thickening near hard-sphere colloidal dispersion, a prototypical wormlike micelle system, and a shear banding wormlike micellar system that also exhibits shear-induced phase separation. In each case, 1-2 plane flow-SANS data provides critical information about the mechanisms underlying the highly nonlinear rheological behavior.