In the chakra system the fourth chakra is the heart chakra at the center of the chest. The emanating color associated with the heart chakra is green. The element associated with it is air. The shape associated with it is the six pointed star, the Magen David, the shield of David. One way to understand what the image of the Magen David communicates is that it says something similar to that which the yin yang symbol does. Both symbols communicate a dynamic tension and relatedness between two opposites. The yin and yang symbol demonstrates that darkness and light exist in relation to each other, share a space, and carry something of the other within itself. The white form and the dark form nestle into each other, and a circle of white exists within the dark as a circle of dark exists within the white. Night and day nestle into one another, as do earth and sky, as do masculine and feminine elements. The Magen David is composed of two triangles overlapping at the center, pulling in opposite directions, the top point of the higher triangle points toward the sky, and the bottom point of the lower triangle points toward toward the earth. The center of the image is composed of a piece of each triangle. The heart of the six-pointed star is six-sided shape deriving from both triangles, essentially yin and yang, earth and sky, feminine principle and masculine principle. The chakra beneath the heart chakra, the solar plexus chakra, is represented as an upward pointing yellow triangle, or sometimes a pyramid. The element associated with it is fire. The chakra above the heart chakra is the throat chakra, represented by a circle, emanating color is blue, and the element is ether. So the heart chakra unites yellow and blue because it is green. The upward reaching triangle of the solar plexus seeks the blue circle of the throat, through the heart, as if the heart could unite both energies.