To determine what is the best aggregate size (i.e. the one that gives optimal colonies with the least amount of differentiation), we recommend performing the aggregate count method at passage and plate a range of aggregate numbers (starting with 300 aggregates per well and plating some wells with less than 300 and some with more). Determine which aggregate number gives you the optimal colony morphology for the passaging schedule you are working with (e.g. 7 days).