There is a critical, unmet scientific need for simultaneous measurement of surface rheological moduli, both shear and bulk, and molecular structure, both in plane and through the interface, across a broad range of interfaces, temperatures, surface area per molecule, and sample preparation DOE neutron scattering user facilities, and international facilities more generally, are currently unable to provide such a sample environment on neutron reflectivity beamlines necessary for the scientific community to develop molecular structure-property relationships for complex fluid interfaces We propose to develop a world-leading sample environment for neutron reflectivity (NR) and grazing incidence neutron scattering (GiSANS) coupled to Interfacial Rheometry applicable to a broad range of soft matter and biological materials across a range of processing conditions Analysis of such data on air-liquid and liquid-liquid interfaces provides Ångström-level detail on the structure of interfaces of relevance to soft matter and biology A research instrument currently under development in the group of Prof Wagner at the University of Delaware will be significantly improved upon to meet the demanding requirements for more general use in national neutron scattering facilities A minimum viable prototype will be demonstrated to meet mechanical, thermal, and chemical environmental specifications appropriate to be deployed on neutron reflectometers at US national neutron scattering facilities Customer needs for neutron, x-ray and individual labs will be established This sample environment will be deployable world-wide on neutron reflectometry beamlines, and will also be readily deployable on X-ray beamlines internationally Additionally, it will be of direct use in numerous commercial and academic research laboratories for its unique interfacial rheology capabilities, which are applicable to studying the critical properties and manufacturing processes of systems including pharmaceuticals, foods, consumer products, paints/coatings, and more Hence, we anticipate a broad potential customer base that includes neutron and x-ray scattering facilities as well as individual research groups studying interfacial systems, in both academic and industrial settings