Lignin nanoparticles (LNPs) have gained a tremendous interest in academic research due to their potential to enhance the performance of technical lignins in many applications, including dispersants, nano-coatings, additives in adhesives, emulsifiers in cosmetics, and many more. LNPs can be produced by different approaches (e.g., acidification, aerosol flow, mechanical treatment, reverse micelle formation), with rapid solvent shifting being among the more popular methods. Here, lignin is dissolved in an organic solvent (e.g., THF, aqueous acetone, etc.) and then rapidly poured into a vigorously stirred anti-solvent (water). It has been hypothesized that the formation of LNPs is mainly driven by the aggregation behavior of lignin due to hydrophobic effects and - interactions of aromatic rings. The size of the resulting LNPs heavily depend on lignin properties (e.g., origin, molar mass, functional group composition, purity), and on the other hand on the synthesis conditions used in the preparation (e.g., solvent and anti-solvent composition, lignin concentration, rate of addition, etc.). The size, shape and surface charge of the LNPs are crucial parameters for successful utilization in various applications. For example, to apply LNPs for drug delivery, particle sizes between 70 and 200 nm are preferred, while for cosmetic applications, particle sizes above 200 nm are favored. The same is true for other applications such as Pickering emulsions where smaller LNPs yield more stable emulsions, whereas in coatings or hybrid materials, it might be not as crucial to have rather small and monodisperse particles. Moreover, particle size and dispersity can have a significant influence on the optical properties of LNPs. Recent studies have shown that a better control of the LNP size opens up new fields of applications in photonic materials. Particle properties (i.e., particle size distributions, shape and morphology) of LNPs are commonly determined by a combination of different analytical methods such as dynamic light scattering (DLS; also referred to as quasi-elastic light scattering (QELS), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and small angle x-ray scattering (SAXS). DLS determines the hydrodynamic radius (Rh)-the radius of a hypothetical sphere with a certain translational diffusion coefficient (Dt)-via the change in scattered light over time caused by the Brownian motion of the particle in solution. In batch mode DLS, the sample is filled into a cuvette and placed in the path of a single-frequency laser beam.