Infarct scar tissue has long been considered inert (acellular, composed simply of fibrillar collagen) and whose function is simply to restore structural integrity to infarcted myocardium and to provide tensile strength that prevents tissue rupture. Technologies of cellular and molecular biology have altered this perspective. Infarct scar is now recognized as living tissue: composed of a persistent population of fibroblast-like cells whose ongoing activity includes a regulation of collagen turnover and scar tissue contraction and which are nourished by a neovasculature. Herein we briefly review these various components of the infarct scar that provide for its dynamic nature and which is relevant to today's interest in preventing heart failure through a rebuilding (regrowing) of myocardial tissue at the infarct size.