How an embryo draws the line between body and germline

Every embryo of an organism that reproduces sexually faces an early and consequential decision: which of its cell lineages will make up the mortal body, and which will become the germline, the lineage that eventually makes eggs or sperm and carries genetic information to the next generation. Get this wrong, and an organism can live but cannot reproduce and, evolutionarily, ceases to exist.

Raccontata daphys.org