Due to the promising potential of evanescent optical waves and surface plasmon polaritons to successfully merge current photonic and electronic technology on the nanoscale, they are generally envisioned as the information carriers of the future. This, however, requires the advanced miniaturization of integrated optical circuitry, which demands great effort not only in fabrication and design, but even more so in the development of accurate control and, above all, a deepest scientific understanding of sub-wavelength-confined light. At present, the thorough understanding of the nanoscale behaviour of evanescent fields and the details of the underlying light-matter interactions are missing, but key elements in modern optoelectronics research.TRUEViEW aims to provide the currently missing fundamental knowledge, by implementing innovative electron imaging techniques as the ultimate tools to directly visualize and characterize photonic and plasmonic nanostructures in both space and time with nanometer and femtosecond resolution. The project takes a bottom-up approach throughout, yielding a systematic and consistent route towards unravelling the working principles of nanoscale-confined optical waves and gaining practical expertise on the manipulation of light in optoelectronic nanostructures. At the same time, the project will pioneer and establish the field of ultrafast electron microscopy in the European research community, as well as newly introducing the novel technique of in-situ Photon-Induced Near-field Electron Microscopy.On the whole, TRUEViEW will lay the groundwork for a myriad of future optoelectronic applications, which include - among many others - sub-wavelength optics, light generation and data storage, nanolithography, quantum computing, quantum cryptography, biophysical spectroscopy and nanosensing. As such, the project will have a strong impact not only all across the scientific board, but also in the European commercial and technological industry.