Schematic representation of the origin and development of megakaryocytes. The multipotent hematopoietic stem cell produces a progenitor cell committed to megakaryocyte differentiation (Meg-CFC), which undergoes mitosis. The Meg-CFC eventually ceases to undergo mitosis and enters endomitosis, during which DNA replication proceeds but neither cytoplasm nor nucleus divides; this gives rise to polyploid immature precursor cells. Upon completion of endomitosis, the immature progenitor cells become large, morphologically identifiable mature megakaryocytes that shed platelets.