Embryonic stem cells (ESCs) are abbreviated as ES, EK, or ESC cells. They are a class of cells isolated from early embryos (before the proto-intestinal stage) or primitive gonads, which have the properties of unlimited proliferation, self-renewal and multidirectional differentiation in vitro in culture. ES cells can be induced to differentiate into almost all cell types of the organism, both in vitro and in vivo environments.