Craniosacral therapy dates back to 1970 and was developed by osteopathic physician John Upledger. The idea is that the whole body responds to the rhythmical activity of the craniosacral system.
During a craniosacral therapy session, a therapist senses subtle motions while looking for any restrictions impeding the free motion of the craniosacral system and various body regions, tissues, organs, and subtle energy systems. Manual techniques using very light touch help release those restrictions.
Craniosacral therapy takes place while you lay on your back. You may wear comfortable clothes, but it can also be done through the sheet and blankets if you are unclothed.
A therapist who has been especially trained in craniosacral therapy will use techniques that will probably include holding your head in various positions and your feet. They slip one hand under your sacrum and hold the other on your belly, holding each position as they gradually move up the spine.
The treatment is very gentle, with an "energy work" component, and should leave you feeling refreshed and balanced.