The structure and orientation dynamics of sepiolite clay fibers about 1000 nm long and 10 nm thick, suspended in an aqueous poly(ehtylene oxide) matrix of 100 000 g/mol molecular mass, have been studied under control extensional and shear flow. A new extensional flow cell developed at the "Laboratoire de Rhéologie" and the combined rheology and small angle x-ray scattering (Rheo-SAXS) set-up available at the European Synchrotron Radiation Facility, have allowed to access to in-situ and time resolved fibers orientations and structure properties in the volume of suspensions under flow. In the volume fractions and shear rate domains for which the suspensions exhibit shear-thinning properties, two regimes of orientation separated by a critical strain rate have been identified under extensional flow.