Magnetic fields are an elementary part of the interstellar medium (ISM) that have a large impact on the dynamics of the ISM on various spatial scales.
Here, I'll talk about the long-standing (and not solved) issue of how to generate magnetically supercritical cloud cores out of the magnetised diffuse medium. Furthermore, I'll discuss how to circumvent the 'magnetic braking catastrophe' which was thought to be a major problem for the formation of protostellar discs.