"In a first, Mitalipov and his privately funded team report that these cloned embryos were grown past an eight-cell size (where earlier attempts had stopped) into a full-blown early embryo, containing hundreds of embryonic stem cells. Embryonic cells taken from these cloned embryos were grown into six colonies of cells, the first successfully grown cloned human embryonic stem cells. The embryos were destroyed in the cell collection process. Some of the cells were successfully prompted to become more specialized skin and heart cells. That is the next step in someday using the cells in "regenerative" medicine, where cells cloned from a patient would be used to grow into transplant organs to treat diseases and injuries such as paralysis. "For stem cell biology, there will be history before this result and then history after it with the study as the dividing line," says stem cell researcher Paul Knoepflerof the University of California, Davis. "No doubt This is a real milestone.""