Found in the Hermetic texts from the Emerald Tablets between the sixth and eight century, it refers to the microcosm and macrosm within and around us.
We are made of the same energies as that of the universe. The same mechanics found in the universe, are also within us. Through quantum super-positioning, the same quantum laws that apply in the universe, also applies to us. The same chemical energies found in the stars such as phosphorus, hydrogen, sodium, Sulfur, magnesium, and iron can be found in almost all living organisms.
What is in the heavens, is also here below on earth. The universe as the macrocosm, we (the Soul) as the microcosm meanwhile the macrocosm also exists within us.