Charles Ridley is known for having refined a version of biodynamic craniosacral work that is nonmedical and nonmechanical. In "Stillness, " he clarifies the three fundamental types of this work -- biomechanical, functional, and biodynamic. He explains the requirements and pitfalls of each model, and how to discern the differences and similarities between them. He guides the practitioner experientially to explore what he is describing, and offers exercises drawn from his own practice to help therapists access directly the whole felt-body sense that connects each individual with the Breath of Life.