The simulation of facial movements is a difficult task because the complex and sophisticated structure of the human head involves the motion, deformation, and contact handling between bio-tissues that are viscoelastic, nonlinear, anisotropic, and structurally heterogeneous. This makes it hard to formulate a mathematical model able to represent the biomechanical inner workings of the face. Nonetheless, high accuracy and precision are required because, as humans, we are used to observe and decode facial expressions from the moment we are born, and we are expert at easily detecting the smallest artifacts in a virtual facial animation.