Injury to the heart (e.g. by a heart attack) will cause irreversible damage. On the other hand, zebrafish can fully recover from a heart attack. Therefore if we can the discover factors that aid the zebrafish to regenerate, we can use this information to understand why heart attack patients cannot properly repair their hearts. In this study the researchers carried this out by examining the DNA and RNA of zebrafish hearts over time as they recover from heart injury. They found many changes both at the DNA and RNA level as the hearts regenerated new tissue. They discovered new factors that are only present during regeneration but are now examining whether modifying the factors either by increasing or reducing its activity would enhance or decrease (respectively) the regenerative ability of the zebrafish.