HMGB2 and myocardial infarction: Cardiomyocyte‐specific HMGB2 knockdown curtails cardiomyocyte proliferation and impairs heart regeneration following apical resection in neonatal mice, while cardiomyocyte‐specific HMGB2 overexpression enhances cardiomyocyte proliferation and facilitates cardiac regeneration and repair in adult mice post‐myocardial infarction.