Essential Thrombocytosis (ET) is chronic blood disease characterised by the overproduction of platelets (thrombocytes) by megakaryocytes in the bone marrow which can progress to acute myeloid leukemia or myelofibrosis. Here we present pictures of bone marrow biopsy smear of an adult female diagnosed with ET. Yellow arrows show clusters of abnormal megakaryocytes which by their presence the diagnosis is confirmed.