The phrase "embryo stage" refers to the very early development of a living organism, typically after fertilization and before it becomes a fully formed being. Full definition
We would expect these cells to have been wiped clean when the fetus's epigenome was reset at the early embryo stage. (newscientist.com)
This mechanism therefore ensures that reprogramming is completed within one cell cycle and protects genomic integrity at the volatile single - cell embryo stage. (sciencedaily.com)
For Noggin protein - treated caps, stage 9 animal cap explants were cultured with 500 nM mouse Noggin protein (Sigma - Aldrich, catalogue number N6784) in 0.7 × MMR and 50 µg / ml gentamicin sulphate and grown to sibling embryo stage 15 for transplantation. (journals.plos.org)