INSERM, UA7, Synchrotron Radiation for Biomedicine (STROBE) 1 article published in JoVE Chemistry Biological Samples Preparation for Speciation at Cryogenic Temperature using High-Resolution X-Ray Absorption Spectroscopy Caroline Bissardon1, Marie-Pierre Isaure2, Emmanuel Lesuisse3, Mauro Rovezzi4,5, Eric Lahera4,5, Olivier Proux4,5, Sylvain Bohic1,6 1University Grenoble Alpes, INSERM UA7, Synchrotron Radiation for Biomedicine (STROBE), 2 This protocol presents a detailed procedure to prepare biological cryosamples for synchrotron-based X-ray absorption spectroscopy experiments. We describe all the steps required to optimize sample preparation and cryopreservation with examples of the protocol with cancer and phytoplankton cells. This method provides a universal standard of sample cryo-preparation.