Platelets play crucial roles in hemostasis, thrombosis, and immunity, but our understanding of their complex biogenesis (thrombopoiesis) is currently incomplete. Deeper insight into the mechanisms of platelet biogenesis inside and outside the body is fundamental for managing hematological disorders as well as development of novel cell-based therapies. Here we address current understanding of in vivo thrombopoiesis, including mechanisms of platelet generation from megakaryocytes …