This paper, by one of the legends of hematology, William Dameshek, and his colleague Edward Miller, is from the inaugural issue of Blood. By studying bone marrow specimens from controls, patients with acute or chronic immune thrombocytopenia, or patients with other thrombocytopenic disorders, the authors concluded that, in idiopathic thrombocytopenic purpura (ITP), production of platelets from megakaryocytes is defective, even while marrow megakaryocytes are greatly increased in number. This defect resolved after splenectomy. The authors appropriately credit E. Frank with having proposed defective platelet production from megakaryocytes in ITP in 1915. The idea that platelet production was defective in ITP was superseded or ignored for decades, but it has now been validated by the therapeutic effectiveness of the thrombopoietin mimetics in ITP.