time-resolved electron diffraction (TRED) emerged from the structural GED, gradually leading to the first successful results in the imaging of the photoinduced dynamics in real time and space. With the construction of the megaelectronvolt ultrafast electron diffraction (MeV-UED) setup at Stanford, the new era of the TRED started, allowing for more efficient and robust visualization of photochemical processes in the femtosecond time-domain using electrons. In the GED technique, the scattering of electrons by molecules is measured as shown in Fig. . The resulting diffraction patterns are converted into intensity functions in the reciprocal space I total (s) = I b (s) + I mol (s) .