In the earliest hours of a fruit fly embryo's existence, a quiet molecular negotiation determines which cells will build a body and which will carry life forward into future generations. Researchers at the Whitehead Institute have discovered that this boundary is not drawn by genes switching on or off, but by a protein called GCL reshaping the chemistry of the cell membrane itself — preparing the terrain before the first germ cells even appear. The finding, rooted in the humble fruit fly, speaks to a deeper truth about how life organizes itself: that the most consequential decisions are often