In the lecture, we will first talk about x-ray quantum optics with nuclei and their sensitivity to gravitation on earth. We then move over to electron diffraction in standing laser waves (Kapitza-Dirac effect), with a focus on spin dynamics in the effect. After a short introduction about the Kapitza-Dirac effect, we will discuss a the formalism of a plane wave expansion, which is common for the description of the effect. We will than talk about some details of the quantum dynamics and move over to some interesting properties of the spin-transfer between electrons and light. Remarks are given about how to transition from time-dependent perturbation theory to covariant perturbation theory, for the case of linear dynamics at low field amplitudes. We will finally look at some more recent developments on the topic regarding focussed laser beams.