Hard X-ray transmission X-ray microscopy (TXM) is an ideal tool for in situ and operando studies of electrochemical systems. The high energy X-rays provides relatively relaxed restrictions on in situ environments enabling high resolution 2D microscopy and tomography (3D microscopy)1 across a large range of pressures and temperatures and in varying gas or liquid environments. The full field geometry of TXM allows imaging at the sub-second time scale, allowing relevant morphological and chemical dynamics to be captured during; for example, battery cycling,2,3 catalysis reactions,4 electrochemical synthesis,5 and corrosion.6,7 This talk will present recent X-ray microscopy results on electrochemical systems studied in situ or operando with a focus on Li-ion and beyond Li-ion battery technologies. In the search for better battery materials, high resolution X-ray microscopy during battery operation is vital in understand and overcoming the failure mechanisms of these materials. Often failures originate as nanometer or sub-nanometer heterogeneities which create a cascade that leads to system failure. TXM can probe the morphological and chemical dynamics of these heterogeneities to understand how and when failure occurs. N. Weker, N. Liu, S. Misra, J. C. Andrews, Y. Cui and M. F. Toney, Energy Environ. Sci. 2014, 7, 2771-2777.Nelson Weker, Y. Li, R. Shanmugam, W. Lai and W. C. Chueh, ChemElectroChem 2015, 2, 1576-1581.Nelson Weker, A. M. Wise, K. Lim, B. Shyam and M. F. Toney, Electrochim. Acta 2017, 247, 977-982.D. Gonzalez-Jimenez, K. Cats, T. Davidian, M. Ruitenbeek, F. Meirer, Y. Liu, J. Nelson, J. C. Andrews, P. Pianetta, F. M. F. de Groot and B. M. Weckhuysen, Angew. Chem. Int. Ed. 2012, 51, 11986-11990.E. R. Tay, A. E. Goode, J. Nelson Weker, A. A. Cruickshank, S. Heutz, A. E. Porter, M. P. Ryan and M. F. Toney, Nanoscale 2016, 8, 1849-1853.A. Koronfel, A. E. Goode, J. Nelson Weker, S. E. R. Tay, C. A. Stitt, T. A. Simoes, J. F. W. Mosselmans, P. Quinn, R. Brydson, A. Hart, Michael F. Toney, A. E. Porter and M. P. Ryan, npj Mater. Degrad. 2018, 2, 8.A. Koronfel, A. E. Goode, M. A. Gomez-Gonzalez, J. Nelson Weker, T. A. Simoes, R. Brydson, P. Quinn, Michael F. Toney, A. Hart, A. E. Porter and M. P. Ryan, accepted to J. Phys. Chem. C. 2019.