Building Blastocysts from Stem Cells.

The blastocyst stage and the subsequent implantation are critical for a successful pregnancy, yet are challenging to study in vivo. In this issue of Stem Cell Reports, Kime et al. (2019) describe a novel way to generate blastocyst-like structures only from pluripotent stem cells. These structures mimic several aspects of the early embryo, offering a new promising tool to study this stage.