Planarians provide a relatively simple model system in which to study stem cell dynamics and regenerative phenomena. As with other systems understanding the dynamics of stem cell and stem cell progeny is crucial in order to get at the molecular mechanisms orchestrating stem cell biology. Planarians have an abundant adult stem cell population that can be observed using Fluorescence-Activated Cell Sorting (FACS). This approach allows different subpopulations of stem cells and their progeny to be monitored and sorted for downstream studies in response to different regenerative scenarios, drug treatments, or RNAi knockdown of genes required for regenerative events.