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Stem cell cultivation. The zygote undergoes successive divisions to morula and then to blastocyst. In the blastocyst, the inner cell mass (ICM) develops into the fetus, whereas the trophectoderm (TE) at its periphery generates the embryonic membranes and placenta. Embryonic stem (ES) cells and trophoblast stem (TS) cells are derived from the ICM and TE, respectively. These stem cells can self-renew and differentiate into multiple lineages.
