The formation of solid inorganic salts from solutions is of fundamental importance for industrial, geological, and biological processes. Here, we review the literature on the fundamentals of inorganic scaling with the goal of elucidating the underlying phenomena observed during thermal desalination processes, mainly multi-stage flash (MSF). We will focus on one of the most common foulants, CaCO3, recognizing that similar phenomena occur for other salts and that behaviors in mixtures with other salts and organic molecules will impact the real world situation. This review will cover a wide range of dimensions, providing views from molecular level to plant scale. In addition to the mechanism and kinetics of scale formation in MSF, we will also review current strategies to control scaling in MSF and highlight directions for future development. •Heterogeneous nucleation is a key step during scale formation.•In situ characterization methods enable enhanced analysis of nucleation kinetics.•Temperature, pH, CO2 partial pressure and seawater composition all affect scaling.•Key factors for heterogeneous nucleation need more investigation.•Anti-scaling coatings could be effective solutions for scaling control.