In humans, the blastocyst is a grouping of 70-100 cells that will eventually become an embryo and placenta. It consists of an inner cell mass, an outer layer of cells, and a fluid-filled cavity. The inner cell mass becomes embryonic stem cells while the outer cell layer later forms the placenta. The embryonic stem cells of the blastocyst are pluripotent, meaning they have the capability to become any possible cell of the body.