1. A method of inducing somatic differentiation of embryonic stem (ES) cells comprising: (a) culturing ES cells in the presence of serum free medium supplemented with growth factors which include epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) to produce neurospheres containing neural progenitor cells, wherein said neurospheres do not express alphafetoprotein; and (b) culturing said neurospheres under conditions that induce somatic differentiation, thereby inducing somatic differentiation of the ES cells.