(1) What is the lunula? There is a white arc-shaped mark located at the one-fifth area under the nail, which is called the lunula, and some people refer to it as the "little sun." The lunula on the nail represents the boundary between yin and yang meridians and is an indicator of the body's essence and energy; hence, it is also known as the health circle. The development of the lunula is influenced by nutrition, environment...