Abstract: The critical current in superconducting systems that lack both time reversal and inversion symmetries is generally non-reciprocal, i.e. unequal in magnitude for opposite current flow directions. This effect — called the superconducting diode effect (SDE) in bulk superconductors and the Josephson diode effect (JDE) in Josephson junctions — has attracted a lot of attention among both experimentalists and theorists, promising many applications for superconducting electronics. Nevertheless, a proper theoretical description of SDE has been challenging both on the phenomenological and microscopic levels, even for the simplest canonical model of the helical non-centrosymmetric superconductor with Rashba spin-orbit coupling (SOC) and in-plane magnetic field. Despite the relative simplicity of the model, several conflicting results have been obtained in the literature, including a prediction of the absence of SDE in the weak field limit. In this talk, I will review some of these controversies and present our resolution, which underscores the subtlety of the effect. Building on this understanding, I will also discuss several new microscopic mechanisms that we proposed for realizing or enhancing the SDE in disordered Rashba superconductors, as well as generic multiphase superconductors like UPt3 and UTe2.