(A) In C. elegans, germ stem cells reside in a niche formed by the distal tip cell (DTC) and are wrapped by the proximal sheath cells (Sh1) as they move proximally and differentiate. The DTC forms protrusions that may communicate with germ stem cells. Gordon et al. discovered that Sh1 cells also have finger-like extensions that intercalate with the DTC and contact progenitors. (B) Cell division takes place in three different compartments within the progenitor zone (PZ): one covered by the DTC (purple) , one at the interface of the DTC and Sh1 (orange), and one covered by Sh1 (green). Divisions are often asymmetric in that each daughter maintains contact with one of DTC or Sh1. (C) Germ cells contacting both the DTC and Sh1 cells contribute a substantial fraction of overall progenitor generation because they have a higher proportion of dividing cells to non-dividing cells compared to the other compartments.