The general strength of electrons is their strong interaction with matter, the compared to X-rays tremendously reduced radiation damage effects, and the fact they are scattered at the electrostatic potential of the sample, thereby allowing to also precisely locate light atoms such as hydrogen and lithium. These properties make electrons an ideal and unique probe for structural investigations of nanometer- and micrometer-sized, radiation sensitive, and low-z materials. Conducting these experiments at linear-accelerators such as REGAE with MeV electrons instead of lab-based devices operating at 100 – 300 keV allows to penetrate trough much thicker samples enabling in-situ and operando experiments. The pulsed structure of the electrons further allows conducting all these investigation in a time-resolved fashion with temporal resolution down to the single digit femtosecond range