Investigations into chemical transformations by mechanochemical milling is currently a fast growing field of chemistry and material science and the scope of such reactions is rapidly expanding. Conducting mechanochemical reactions in closed reaction vessels is however, limiting investigation into their course and consequently, their mechanisms are largely unknown. The SystForSynt project proposal is to address this very issue in the realm or organic transformations. We propose to conduct research in four work packages, that we recognise as highly significant, and which include verification of the Hammett correlation, understanding of liquid catalysis in liquid-assisted mechanochemical reactions, the transferability of mechanisms from milling to extrusion processing and the dynamics of atomic and molecular exchange between processed particles and finally, organic rearrangement and radical reactions. To achieve this, the SystForSynt project will employ is situ monitoring techniques based on Raman spectroscopy and powder X-ray diffraction, which provide a direct insight into the reaction course without interrupting the milling process, and which we have pioneered. In addition, we will use isotope labelled solids to monitor the dynamics of milled solids and any specific atomic migrations. Results of the SystForSynt project are expected to significantly advance understanding of mechanochemistry, which will eventually allow mechanochemistry to position itself as a viable processing approach in a low-waste, atom- and energy-efficient synthesis in the future.