A number of studies are briefly reviewed dealing with hot stage processing of slags, i.e. additions during the molten state and variations of the cooling path, and the influence on the microstructure and properties of solidified slags. Emphasis is placed on research and developments in the last five years, although other works that created the thinking framework for several of the current practices are also mentioned. The additions include: a) quartz sand with concurrent oxygen injection for the minimisation of free CaO and MgO, b) various materials for the modification of the composition of liquid blast furnace slag after tapping, c) borates and boron wastes and their distribution in both synthetic and industrial stainless steel slags, d) phosphates in stainless steel slags and their distribution in BOF slags e) waste glass and fly ash for the stabilisation of stainless steel slags, f) K2CO3 for the production of potassium silicate fertiliser from steelmaking slag and g) bauxite, Al2O3 containing residues and aluminium metal that enhance the Cr recovery and minimise leaching in EAF slags. In terms of cooling, the effect of cooling rate on the final mineralogy, as a way to stabilise stainless steel slags and to control free lime formation in BOF slags, is presented. A more in-depth discussion regarding leaching performance, which has been identified as a key issue in slag valorisation, is also taking place. Although it is acknowledged that many research questions are still open and that both technical and economical barriers exist, it is strongly believed that a conscious hot stage processing step can both increase slag utilisation rates and make higher value applications achievable.