This book provides relevant information on the excitation-contraction coupling process in cardiac muscle cells and a special set of data indicating that there is a pathway for activating the contractile machinery that is independent of calcium ion signaling. Eugenol, an essential oil, was the biological tool that enabled us to identify the existence of this calcium-independent pathway capable of generating a large amount of force in an isometric state. The data indicate that there is a sequence of intracellular signaling pathways, which have not yet been fully unraveled, and which may enable a molecular description of the phenomena that lead to stiffness syndrome in the future.