The regenerative potential of cardiomyocytes is controversial, particularly within the adult heart, as it is unclear if cardiomyocytes retain the ability to proliferate. Since they are mostly post-mitotic and highly specialized, studying the cell cycle in cardiac myocytes is confounded. This study provides a cardiac-specific tool named Fluorescence Ubiquitin Cell Cycle Indicator (FUCCI) to visualize cardiomyocyte cell cycle events. FUCCI works based on cell cycle regulatory proteins, using Geminin and Cdt1, which are substrates of two important ubiquitin ligases, fused to two fluorescent proteins. Ubiquitin ligases oscillate between two distinct phases of the cell cycle, G1 and G2/S/M phases. Here we examine cardiomyocyte cell cycling during development and following ischemic myocardial injury in an attempt to elucidate the regenerative potential of cardiomyocytes.