Creating patient specific blood cells will enable many, many applications - especially in an era of immune therapies. Even the simple ability to greatly multiply the number of white blood cells in a patient's body for a short while can be profoundly beneficial. Here is an update on progress towards engineered blood cells made to order: "In an advance that could help transform embryonic stem cells into a multipurpose medical tool, [scientists] have transformed these versatile cells into progenitors of white blood cells and into six types of mature white blood and immune cells. While clinical use is some years away, the new technique could produce cells with enormous potential for studying the development and treatment of disease. The technique works equally well with stem cells grown from an embryo and with adult pluripotent stem cells, which are derived from adult cells that have been converted until they resemble embryonic stem cells. If the adult cells came from people with certain bone marrow diseases, the new technique could produce blood cells with specific defects. It could also be used to grow specific varieties of immune cells that could target specific infections or tumors."