Stable isotopes are powerful tools for studying the transport and transformation of water, carbon, and nutrients. Their use has enabled new process understanding of the critical zone and the soil-plant-atmosphere continuum. Furthermore, new methodological and technological developments have facilitated using stable isotopes to trace system exchanges and feedback processes on many levels from micro scale processes to regional scale changes. Thus, new opportunities and insights have emerged, supporting increasingly interdisciplinary perspectives on critical zone processes. This session aims to bridge bio-hydro-geo-eco communities by addressing the current state of understanding in critical zone stable-isotope methods and applications. Studies that cross disciplinary boundaries and use novel approaches to improve process understanding are especially welcome. This session also encourages presentations of opinions, perspectives, and syntheses that guide the critical zone stable isotope community.