  We study the formation and growth of equilibrium clusters in a suspension of
weakly-charged colloidal particles and small non-adsorbing polymers. The
effective potential is characterised by a short-range attraction and a
long-range repulsion. The size, shape and local structure of the clusters are
studied using three-dimensional particle microscopy. We observe a rapid growth
in the mean cluster size and the average number of nearest neighbours
approaching the gel boundary.
