It is now generally accepted that some of the major meteor showers that are observed on Earth are caused when the Earth passes through a stream of small grains that have been ejected from specific cometary nuclei. What is observed depends on the location and distribution of these dust grains or meteoroids. These depend primarily on two factors, the meteoroid ejection process and the subsequent dynamical evolution of the meteoroids. Provided the two effects can be disentangled, then the former can give valuable evidence regarding processes ongoing in a cometary nucleus. The main aim of this review talk is to discuss our current understanding of all of these processes and, through this to deduce as much as is feasible about cometary nuclei.