The flag of South Korea, or Taegeukgi was taken from the Chinese design of the yin and yang symbol and has three parts: a white background; a red and blue taegeuk ("Taijitu" or "Yin and Yang") in the center; and four black trigrams, one in each corner of the flag.
The four trigrams originate in the Chinese book I Ching, representing the four Chinese philosophical ideas about the universe: harmony, symmetry, balance, circulation. The general design of the flag also derives from the traditional use of the tricolor symbol (red, blue and yellow) by Koreans starting from the early era of Korean history. The white background symbolizes "cleanliness of the people." The taegeuk represents the origin of all things in the universe; holding the two principles of "Yin", the negative aspect rendered in blue, and "Yang", the positive aspect rendered in red, in perfect balance. Together, they represent a continuous movement within infinity, the two merging as one.
Traditionally, the four trigrams are related to the Five Elements of fire, water, earth, wood, and metal. An analogy could also be drawn with the four western classical elements.