Abstract: The totipotency of somatic cells is one of the key problems in biology, which has been debated for more than a hundred years after being raised by Weisman in the middle of 19 centry. Recently, studies on this problem seem to be greatly improved due to the breakthrough in genetic engineering researches. According to recent opinions, the totipotency of somatic cells is not the same as the expression of totipotency. After possessing the ability of totipotency, the somatic cell can start the expression of totipotency only if being promoted by some factors.