Many simulation studies seek to gain an understanding of nucleation without directly simulating the process. These types of simulations are usually the cheapest as the steady-state solution behaviour can be achieved readily in standard MD simulations. Often, though, enhanced sampling techniques (see section 4.2) are also used to determine the thermodynamic stability of associated species. In complex solutions, simulations have provided information on the species potentially involved in nucleation; careful analysis of these species and their assembly can aid the classification of nucleation pathways. For example, Demichelis et al. performed metadynamics simulations (described in section 4.2) to confirm the relative stability of calcium phosphate complexes as the first associates to form in solution and thought to be directly involved in mineral nucleation from experiments. Simulations have also shed light on structural building units that act as precursors in the nucleation of metal-organic frameworks and the complexes that assemble to form inorganic functional materials.