The invention is concerned with producing differentiated cells, tissues and organs from pluripotent and mutlipotent cells. The methods of the invention are particularly useful for producing differentiated cells from pluripotent cells wherein communication between the cells of more than one embryonic germ layer or more than one organ system are required for development along a specific cell lineage. The invention methods are effected by in vivo or in vitro culturing of embryonic and developing or developed allogeneic or xenogeneic cells.
