Table 1.

Summary of hPSC-based in vitro embryo models.

Embryo Model	Reference	Structure	In Vivo Equivalent	In Vitro Development
Gastrulation micropatterned colony	[104,105]	2D	Gastrulation: germ layer patterning and gastrulation “movements”	hESCs are forced to grow in a confined geometry on micropatterned coverslips; treatment of hESCs with BMP4 triggers self-organized spatial patterns of an outer trophectoderm-like ring, an inner ectodermal circle and a ring of mesendoderm in between, where cells undergo EMT and migrate inwards mimicking gastrulation
Asymmetric early post-implantation epiblast	[106]	3D	Early post-implantation, pre-gastrulation: day 10 human epiblast	hESCs dispersed in hydrogel supplemented with Matrigel form lumenal sacs, which break the anterior–posterior symmetry upon BMP4 treatment and polarize into ectoderm and mesoderm
Post-implantation amniotic sac embryoid (PASE)	[107,108,109,110]	3D	Post-implantation, gastrulation: post-implantation development until days 13–19 (including epiblast cyst formation at days 6–7, asymmetric sac development at days 7–13 and the onset of gastrulation at days 13-19)	hESCs form an amniotic sac, with amniotic ectoderm, an amniotic cavity and an embryonic disc; the embryonic disc develops into a primitive streak-like region with cells undergoing EMT and disseminating into the microenvironment
Gastruloid	[111]	3D	Post-gastrulation: 72 h gastruloids show features of late Carnegie-stage 8 embryos (days 17–19) to early Carnegie stage 9 embryos (days 19–21)	hESCs are treated with Chiron, a WNT agonist, before seeding in low-adherence plates; gene expression studies of the so formed gastruloids reveal evidence for derivatives of the three germ layers organized in a spatiotemporal manner