The crystallisation process has been used for centuries as a purification and separation step for various applications. Therefore, it is surprising that empirical models rather than fundamental understanding still govern the comprehension of crystallisation's underpinning mechanisms and kinetics. What is well established is that nucleation and crystal growth are the two main steps contributing to the crystallisation process. However, the microscopic mechanism of the formation of the nuclei and how they subsequently evolve into crystals is still unclear . Two widely popular models are used to describe the crystallisation process: classical nucleation theory and non-classical theory. The former states that density and order fluctuations in the solution cause the formation of crystal-like clusters, which in turn result in nuclei that gradually grow into the crystal form defined by the packing of the cluster. The non-classical theory proposes that the clusters first formed are liquid like, and crystalline order is only introduced later when they grow into nuclei. One widely used model system for investigating crystallisation is the MgSO 4 -H 2 O system.