Spontaneous contraction of a coupled neonate myocyte and miPS-CM. Time course of the spontaneous contraction of a microcontact-printed µtissue composed of a coupled miPS-CM and a mouse neonate ventricular myocyte adhered to compliant hydrogel, visualized by DIC imaging (top). Corresponding substrate displacement (middle) and traction stress (bottom) heat maps resulting from TFM. Solid white outline indicates cellular boundary.