We consider two processes whereby the mean size of a nanoparticle dispersion is modified; growth and aggregation. Dynamics of these processes can be monitored, indirectly, by spectroscopies such as UV-visible absorption, microscopy such as transmission electron microscopy (TEM) or by dynamic light scattering (DLS). We are now exploring a new method based on imaging (video capture) of Mie light scattering processes (Halo, LM10 instrument) that allows direct space / real time monitoring of the dynamic behaviour of colloidal particles in a fluid. The technique allows the analysis of a representative subset of particles or of individual discrete particles, one at a time. We have designed nanoparticle systems where growth or aggregation create pronounced and measurable effects on their perceived Brownian motion which can be detected by nanoparticle tracking analysis (NTA) software. Gold nanoparticles with a mean diameter of 10 nm were grown larger using electroless plating. In addition, gold nanoparticles in a range of sizes (10 - 50 nm) were dimerised in a controlled way using a novel bi-functional ligand. The evolution of size and structure in both sets of experiments were confirmed by TEM and, together with data from DLS & UVvis, were correlated with that from the new method. Figure 1: Schematic to illustrate the growth (A) and aggregation (B) processes investigated. The insets to the right of (B) show the change in scattering pattern observed upon cluster formation.