The microscopic properties and switching dynamics of interface-based memristive devices will be comprehensively determined toward fundamental understanding and improvement of their function. To this end, the two complementary cutting-edge methods Transmission Electron Microscopy and synchrotron-based Photoelectron Spectroscopy will be combined in multiscale and in operando analyses of structural, electronic, and chemical characteristics. The focus is on metal-oxide and transition-metal dichalcogenide-based memristive devices as well as particle systems and piezo field-effect transistors.