The development and formation of various types of BLOOD CELLS. Hematopoiesis can take place in the BONE MARROW (medullary) or outside the bone marrow (HEMATOPOIESIS, EXTRAMEDULLARY).

Synonyms: Medullary Hematopoiesis, Hematopoiesis, Haematopoiesis, Hematopoiesis, Medullary