Yin yoga gently stretches the connective tissues of the body, rather than the muscles. It's complementary to "yang" yoga, but time consuming. There isn't that much out there about it yet and this was a pretty good introduction. The author jumps into meridians, metta meditation, mantras, chakras, and acupuncture points along with the asanas. I haven't tried that CD, but will probably get a copy of the sequences for reference.