Homogeneous nucleation (HON) occurs in the bulk of a supersaturated solution and can be controlled by changing the solution environment. As well as temperature and pressure control, solution additives may affect the nucleation behaviour. While the rates for HON can be predicted using a suitable theory/model, the location where nucleation occurs cannot be determined a priori. HON requires specific conditions for it to occur and is much less prevalent in nature than heterogeneous nucleation (HEN). In HEN, crystal nucleation is facilitated by interfaces-usually a solid submerged in the solution phase. Surfaces can act as nucleants to direct the site-specific crystallisation of particular crystal polymorphs or, more generally, enhance the rates for crystallization. The direct simulation of heterogeneous nucleation is a daunting task, as, in general, information on the local structure of the surfaces promoting nucleation is not available. Hence, while the methods discussed in this review are, in principle, applicable to the study of heterogeneous nucleation, as shown, i.e. by the recent works on heterogeneous ice nucleation ,