Abstract The ability to regenerate organs and appendages is not universal among animals. Humans have a rather limited capacity to regenerate after an injury, while other vertebrates such as the zebrafish are capable of regenerating many anatomical structures. It is unknown why different vertebrates have such differences in regenerative capacity, so studying animal models that do regenerate will allow us to know what is needed to regenerate. Zebrafish research is not only able to tell us what mechanisms are involved in regeneration, but it also shows us that there are different regeneration strategies: some use stem cells while other create progenitors from differentiated tissue cells. This article details how zebrafish uses and regulates either differentiated tissue cells or stem cells to regenerate. We focus on four structures ? fin appendage, brain, spinal cord and heart ? and describe how current cell and molecular discoveries from these regenerating fish structures contribute to our understanding of general principles of regenerative biology. Key Concepts The zebrafish is a remarkable in vivo model to understand the stem/progenitor cell biology and molecular mechanisms involved in appendage and organ regeneration. Studying how the zebrafish regenerates its fins, its nervous system and its heart will provide information on how endogenous cell populations (whether fully differentiated or stem cells) are activated and concertedly controlled to regenerate compound structures. Different zebrafish tissues use different strategies to regenerate: some convert differentiated tissue cells to progenitor cells while other draw from stem cell pools. Zebrafish appendages and hearts regenerate primarily from the residual differentiated tissues. Zebrafish nervous tissue regenerates from resident stem cell populations.