The stem cells that give rise to other blood cells are known as Hematopoietic Stem Cells (HSCs). Haematopoiesis is the name for this process. In vertebrates, the first definitive HSCs emerge from the embryonic aorta's ventral endothelium wall in the (midgestational) aorta-gonad-mesonephros area, a process known as endothelial-to-hematopoietic transition. Adults' haematopoiesis takes place in the red bone marrow, which is found in the centre of most bones. The mesoderm layer of the embryo is where the red bone marrow comes from. All adult blood cells are created by the process of haematopoiesis. It must strike a balance between massive production demands (the average human produces more than 500 billion blood cells each day) and the requirement to control the quantity of different blood cell types in circulation. The vast bulk of hematopoiesis in vertebrates occurs in the bone marrow and is formed from a few numbers of multipotent hematopoietic stem cells capable of significant self-renewal. Myeloid and lymphoid lines of hematopoietic stem cells give rise to different types of blood cells. Dendritic cell development involves both myeloid and lymphoid lineages. Monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, and megakaryocytes are all myeloid cells, as are platelets. T cells, B cells, natural killer cells, and innate lymphoid cells are all lymphoid cells. Since HSCs were initially discovered in 1961, the definition of hematopoietic stem cell has evolved. Long- and short-term regeneration cells, as well as committed multipotent, oligopotent, and unipotent progenitors, are found in the hematopoietic tissue. In myeloid tissue, hematopoietic stem cells account for 1 in 10,000 cells