In addition to stretching the connective tissue, Yin yoga asanas (poses) also help to stimulate the flow of chi energy through the meridians of the body; similar to acupuncture. Since Yin yoga focuses on the lower, or yin, half of the body (from the waist down), the asanas work to stimulate the lower body meridians - liver, kidney, stomach, urinary bladder, and gallbladder. By stimulating the meridians in this way, we can help to take care of their associated organ. The most important of these, according to Traditional Chinese Medicine, are the kidneys as they are the source of all health.
To help stimulate the kidney meridian try dragonfly pose. Sit with your legs spread apart and fold forward. The spine can round as it needs to and the hands can be wherever is most comfortable. Keep the muscles in the legs relaxed and try to hold the pose for at least three minutes. Focus on the breath and try to direct it to any areas that feel particularly tight or restricted.
Yin Yoga stretches the body in ways that other forms of yoga do not. Most other forms of yoga are focused on stretching the muscles of the body. Yin Yoga works to stretch the connective tissues of the body that are found in the joints and surrounding the muscles; particularly the joints of the spine. Just like muscles, if you do not use the joints of the body you will lose them; they will become fixated and immobile. What does this mean for you? It means that as you reach old age, you may find yourself unable to stand up straight; you may become hunched over because you have lost the ability to use the joints in the low back.
A great pose to start to counter this affect is with Caterpillar pose (seated forward bend). Just sit on the floor with your legs in front of you and fold the upper body forward keeping the muscles relaxed so the joints can take the stretch. If you find that folding forward is a challenge, you can also do this pose standing up by dangling the top half of the body forward, like you were trying to touch your toes. The key is to hold the pose for at least two minutes; more if you comfortably can.