There are nearly two million Americans living with a limb amputation and even with the best modern surgical intervention, a human limb does not regenerate. Amazingly, however, the amputation of a child's fingertip can regenerate, and the medical implication of understanding the molecular basis of this innate process is incredibly important for regenerative medicine efforts. The mouse digit tip, which similarly regenerates following amputation, is a powerful experimental system and serves as an excellent proxy for human limb regeneration. Upon amputation, the digit tip undergoes epimorphic regeneration, a process involving the recruitment and proliferation of a mass of heterogeneous, lineage-restricted progenitor cells, termed the blastema, which gives rise to all of the regenerate tissue except the skin. Understanding how cells are recruited to form a blastema, how they remain proliferative, and how they organize and differentiate into appropriate tissues, are some of the key questions in regenerative biology. My lab uses mouse genetics to determine the molecular pathways and cells types necessary for blastema formation and successful digit tip regeneration, as well as to better understand each of the individual tissues within the digit tip.