Specialized stem cells are cells that can only produce the same type as themselves; where as undifferentiated cell can produce any type of cell (But there are a limited number of cells that it can produce)."Embryonic stem cells are pluripotent, meaning they are able to grow (i.e. differentiate) into all derivatives of the three primary germ layers: ectoderm, endoderm and mesoderm. In other words, they can develop into each of the more than 200 cell types of the adult body as long as they are specified to do so. Embryonic stem cells are distinguished by two distinctive properties: their pluripotency, and their ability to replicate indefinitely. ES cells are pluripotent, that is, they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm. These include each of the more than 220 cell types in the adult body. Pluripotency distinguishes embryonic stem cells from adult stem cells found in adults; while embryonic stem cells can generate all cell types in the body, adult stem cells are multipotent and can produce only a limited number of cell types. Additionally, under defined conditions, embryonic stem cells are capable of propagating themselves indefinitely." (see reference 1 on home page)