 First, following Rossant’ summary, the scientists present had extensive discussion about strategies for improving the rates of chimerism. Considered purely as a scientific problem, there seems to be significant interest in overcoming the current limitations which prevent human cells from having much of an impact. Moreover, exceptions to Rossant’s generalization were mentioned later in the workshop, including research in which human neural progenitor cells proliferated “extensively” when injected into the adult mouse brain, research in which some cell lineages continued to act like the donor-species cell regardless of the surrounding animal environment, and research in which human-derived glial progenitor cells outcompeted the corresponding mouse glial, “ultimately dominating the brain”.