Embryoblasts refer to the inner cell mass in the early development of embryos. They play a key role in forming the definitive structures of the fetus. 

Human embryonic stem cells, which are the cells of the embryoblasts, are pluripotent. They are capable of differentiating into any of the intermediate progenitor cell types that turn into adult cell lines eventually. In addition, human embryonic stem cells are immortal. They can divide and grow infinitely, without undergoing any change in terms of cellular aging or differentiation.