Lignin is one the most abundant biopolymers and has due to its sustainability and accessibility generated interest in industrial as well as research communities. Lignin nanoparticles (LNPs) have emerged within the past few years as a promising type of colloidal materials for applications ranging from coatings and composites to biomedical adhesives.1 While ex situ data has given some insight in the growth mechanism of LNPs, in situ measurements have not been performed before. We thus aim on elucidating the growth mechanism of LNPs using time-resolved SAXS data. We intend to extract information on molecular arrangement, packing density, and porosity of LNPs.