In 1894, Hans Driesch cloned a sea urchin through inducing twinning by shaking an embryonic sea urchin in a beaker full of sea water until the embryo cleaved into two distinct embryos. In 1902, Hans Spemann cloned a salamander embryo through inducing twinning as well, using a hair from his infant son as a noose to divide the embryo. In 1928, Spemann successfully cloned a salamander using nuclear transfer. This involved enucleating a single-celled salamander embryo and inserting it with the nucleus of a differentiated salamander embryonic cell. In 1951, Robert Briggs and Thomas Kling, using Spemann’s methods of embryonic nucleus transfer, successfully cloned frogs. In 1962, John Gurdon announced that he too had successfully cloned frogs but, unlike Briggs and Kling’s method, he did so by transferring differentiated intestinal nuclei from feeding tadpoles (Wilmut et al. , 2000). Gurdon’s successful use of differentiated nuclei, rather than the embryonic nuclei used by Briggs and Kling, was particularly surprising to the scientific community. Because embryonic cells are undifferentiated, and therefore extremely malleable, it was not too surprising that transferred embryonic nuclei produced distinct embryos when inserted into an enucleated oocyte. However, inciting differentiated nuclei to behave as undifferentiated nuclei was thought to be impossible, since the conventional wisdom at the time was that once a cell was differentiated (., once it became a cardiac cell, a liver cell, or a blood cell) it could never reverse into an undifferentiated state. It was for this reason that, for a long time, creating a cloned embryo from adult somatic cells was thought to be impossible – it would require taking long-time differentiated cells and getting them to behave like the totipotent cells (cells that are able to differentiate into any cell type, including the ability to form an entirely distinct organism) found in newly fertilized eggs.