Abstract Neutron reflectometry offers unique benefits for nanolayer research in green chemistry by providing accurate depth profiles of thin films and interfaces with subnanometer precision, under in operando condition, of active material in their native environments. Advantages of this technique include sensitivity to light elements, isotopic contrast control (which enables elemental depth profiles or labeling of specific features or reactants of interest), and the ability to penetrate complex and multimodal sample environments. This chapter focuses on the most stringent example in green chemistry, in operando electrochemistry. Because neutron reflectometry is not widely utilized, this chapter provides an introduction, literature review, theoretical basis, practical guides to data collection and analysis, examples, best practices, and future advances, with the goal of making this technique more comprehensible by scientists reviewing or applying neutron reflectometry research results, and making it more accessible to a wider range of experimenters.