Muscle stem cells are the resident adult stem cells of skeletal muscle. Upon muscle injury, these stem cells receive niche signals to activate, exit quiescence and re-enter the cell cycle to undergo proliferation. The subsequent daughter cells undergo a process of asymmetric division whereby one is committed to myogenic lineage progression, differentiating into myocytes which fuse together to form muscle fibers, constituting the muscle tissue. Meanwhile, the other daughter cell returns to quiescence, thereby preserving the stem cell reserve for future muscle repair. One major obstacle to studying quiescence has been accessing these stem cells. Satellite cell quiescence has largely relied upon isolating them from uninjured muscles, assuming they remain unperturbed. However, satellite cells rapidly activate upon dissociation from their niche during the dissociation process. The Cheung Laboratory has successfully isolated quiescent satellite cells using our in situ fixation technique. Freshly isolated satellite cells, traditionally isolated and thought to represent quiescent satellite cells, showed early signs of activation. We have since identified these freshly isolated cells as early activated satellite cells. Therefore the Cheung Laboratory is focused on examining the post-transcriptional mechanisms underlying satellite cell activation and muscle regeneration.