The theory of the five elements has an interesting history and is utilized in the different forms of acupuncture very differently. It seems that some forms, Japanese in particular (including Shiatsu), take it more seriously and it is absolutely instrumental to diagnosis. TCM seems to take it with a grain of salt. Mostly they use it to help explain the etiology of disease and to associate symptoms or signs to particular organ pathologies found in the five element chart.

History

The theory of five elements or wu xing, was most likely conceived in or around the Warring States Period (476 - 221 BC) by someone named Zou Yen. Interestingly, many translators think that using the term "elements" is almost wrong. Unschuld translates it as "phase" and this seems to me as the best translation yet, although it seems elements has stuck in people's heads and thus it isn't going anywhere. By calling them phases it allures more to the processes that are occurring in both nature and the microcosm that is the body. Particularly it better explains the motion of the generating and controlling cycle (see below). In early texts these same five things are also referred to as basic materials of the universe with an addition of grain as a sixth, so I guess they can be thought of in both ways. Keep the term "phase" in mind though as you learn more.

Five Element Correspondences

Without further adieu here they are, pretty much unchanged from the way it is in the Nan Jing (Yellow Emperor's Classic of Internal Medicine).

Five Elements Wood Fire Earth Metal Water
Seasons Spring Summer Late Summer Autumn Winter
Environment Wind Heat Damp Dry Cold
Zang Liver Heart Spleen Lung Kidney
Fu Gallbladder Small Intestine Stomach Large Intestine Bladder
Directions East South Middle West North
Tastes Sour Bitter Sweet Pungent Salty
Sense Organs Eye Tongue Mouth Nose Ear
Tissues Tendon Vessel Muscle Skin and Hair Bone
Emotions Anger Joy Worry * Grief Fear

Quick note: pay attention to the seasons being the first on the list. The Earth element or phase has an interesting position here. In this table it is denoted as Late Summer. In parts of the Nei Jing it is said that it also corresponds to the time in between the seasons.

Movement of the Five Phases

Generating CycleThe five phases have a flow in which they move called the Generating Cycle. Again looking at the seasons, put the phases in order by season and you get the image to your right. (I myself wonder if this cycle was originally formed from the concept of Earth being Late Summer or if that was extrapolated later to give some reasoning for this cycle.) Starting with water (a good way to remember it), water generates wood, wood generates fire, fire generates earth, earth generates metal, and metal generates water.