It is based on the theory that every cell in a healthy body expresses a rhythmic movement which is fundamental to life - and which has been called craniosacral movement. At the core of the body the cerebrospinal fluid, which bathes and cushions the brain and spinal cord, expresses this motion in a tide-like ebb and flow; while bones, organs and other structures in the body each follow their own particular pattern of movement. This motion is so subtle that it is barely measurable with instruments, but the hands of a trained therapist are able to perceive it. In response to physical knocks or emotional stress, the body's tissues contract. Any stresses, tensions or traumas which have been 'stored' in the body in this way will restrict the body's functioning - and these show up in the way the craniosacral motion is expressed. Craniosacral therapists are trained to feel this subtle motion in the body, and can use it to identify areas where there is congestion or restriction. In this way they can identify the possible origin of a problem. Using the hands to reflect back to the body the pattern it is holding, the therapist provides an opportunity for the body to let go of its restrictive pattern and return to an easier mode of functioning.