Different growth modes of Au nanoparticles in an aqueous solution of HAuCl₄ and sodium citrate starting from 4nm citrate-capped seeds. Initially larger particles grow in size while smaller ones dissolve and aggregates merge and coarsen. As the movie progresses, ligand capping breaks down and individual particles grow on dendtrites that collapse into new particles. Video 4x normal speed.Imaging credits: M.H. Nielsen, J.R.I. Lee, T.Y.J. Han, J.J. De Yoreo, Molecular Foundry, Lawrence Berkeley National Laboratory (Unpublished result).