The Seed of Life contains 7 overlapping circles to complete the seal. 7 is a prominent number in the Universe, 7 days of the week, 7 wanderers, 7 notes in a scale, 7 chakras, 7 shells in the atom, 7 metals of antiquity, 7 colours of the rainbow, 7 layers of skin, 7 seas, 7 year cycle, 7 days of creation?