In most organisms, primordial germ cells (PGCs) are set-aside early during embryogenesis. Subsequently, PGCs migrate through the embryo, associate with somatic gonadal cells and form the gonad. While PGCs seem highly specialized, their products are the ultimate stem cells that generate a complete organism generation after generation. Our long-term goal is to functionally dissect the germ cell life cycle in Drosophila. So far our genetic studies indicate that germ cell specification requires transcriptional silencing of the future germ cell nucleus and repression of the somatic cellularization program. We find that lipid signaling plays a critical role for migrating PGCs. Lipid distribution within the embryo and lipid uptake by PGCs provides timing and directionality to PGCs. Finally, our studies support the idea that there is a surprising equivalence among the gene functions that control stem cell potential in PGCs and adult germ line stem cells and that reciprocal signaling between germ cells and somatic support cells regulates the number of stem cells available to fill adult stem cell niches.