Heamatopoietic stem cells are the cells in bone marrow that create blood cells, both red blood cells and white blood cells. They are most highly concentrated in the pelvis, sternum and both femurs. They work on a complicated feedback system that creates those cells depending on how many cells already exist and any particular need the body might have, such as an infection. In total, these cells created roughly 500 billion cells every day. These cells are non-differentiated and are each capable of creating any type of blood cell.