Stem cell systems and regenerative mechanisms are nearly as diverse as animals themselves. This diversity resulted from the differential retention and elaboration of primitive features, and acquisition of new ones in different lineages over evolutionary time. Hence, only comparative studies can provide an integrative image. Recent progress in Hydractinia research positions this animal as an interesting model organism to study any aspect of cell and developmental biology. In particular, Hydractinia’s sessile nature and optical translucence facilitate in vivo studies at single cell resolution. Alongside its three main cnidarian co-players, Hydra, Nematostella and Clytia, Hydractinia is ready to provide new and exciting insights into animal stem cell biology, regeneration and their evolution.