Supercritical fluid assisted sprays for particle generation are widely researched in groups all over the world. Most of the research results follow an empirical approach, trying to bring process conditions into a correlation with product properties. In many cases, a deeper understanding of what is happening in the single unit steps of such processes is missing. Nearly all spray processes using supercritical fluids can be subdivided into the individual steps liquefaction, dosing, mixing and particle formation. This article discusses how far these single steps are developed and understood, and highlights which parameters and conditions along the unit operations of the PGSS process influence particle formation.