This document discusses using photo-controlled chemicals to direct cardiac tissue growth and function. Specifically, it examines: 1) Using azobenzene derivatives that suppress cardiac excitation in response to light, allowing control of propagation speed and patterning of waves. 2) Creating engineered cardiac tissues on nanofiber scaffolds for alignment and precise positioning of cells. 3) Developing 3D cardiac tissues and whole heart preparations that demonstrate reversible light-controlled excitation, as well as tissues derived from pluripotent stem cells.