Adult hematopoietic stem cells have a remarkable developmental plasticity — bone marrow cells can generate hepatocytes that repopulate the liver of mice with fumarylacetoacetate hydrolase deficiency (Fah^-/-) and correct this liver disease. It has been unclear if hepatocytes derived from bone marrow arise from changing potency through cell fusion or by direct differentiation of hematopoietic stem cells. Two papers in the March 31 Advanced Online Nature show that regenerating liver nodules in Fah^-/- transplant recipient mice are derived from donor hematopoietic cells that fused with host hepatocytes, and not from trans-differentiating hematopoietic stem cells or hepatic stem cells present in bone marrow.