The Law of Root and Branch
The substance of the elements of reality in the first, Uppermost world is purer than in all the ones below it. And the substance of the elements of reality in the second world [that comes after it] is coarser than in that of the first world, but purer than all that is of a lower degree.
This continues similarly down to this world before us, whose substance of the elements in reality is coarser and darker than in all the worlds preceding it. However, the shapes and the elements of reality and all their occurrences come unchanged and equal in every world, both in quantity and quality. They compared it to the conduct of a seal and its imprint: all the shapes in the seal [the Upper World] are perfectly transferred in every detail and intricacy to the imprinted object [the lower world].
– Baal HaSulam, “The Essence of the Wisdom of Kabbalah”