Haematopoiesis (; from Ancient Greek αἷμα (haîma) 'blood' and ποιεῖν (poieîn) 'to make'; also hematopoiesis in American English, sometimes h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. In a healthy adult human, roughly ten billion (1010) to a hundred billion (1011) new blood cells are produced per day, in order to maintain steady state levels in the peripheral circulation. Source: Wikipedia (en)