Stunning alignment of rat neonatal cardiomyocytes to a fibronectin pattern printed onto the silicone substrate prior to cell seeding. Rat neonatal cardiomyocytes are particularly responsive to extracellular matrix (ECM) cues when seeded immediately following their harvest from the heart. Trypsinized cells only adhere to the culture dish if ECM proteins such as fibronectin are present, and within 3 days after seeding the cells align their myofibrils to the main direction of the protein distribution. This can be exploited to produce artificial muscle sheets as neighboring cells form gap junctions allowing electrotonic spread and synchronous contraction in the direction of myofibril alignment (cf. Feinberg et al. 2007). Green: Actin in Myofibrils (Phalloidin-GFP); Blue: Cell nuclei (DAPI); Scale: The nuclei measure 10-15µm along their major axis.