From earlier sources, the Kabbalists of Safed, and in particular Cordovero, had adopted the doctrine of four worlds placed between the En-Sof and our earthly cosmos—a doctrine of which no trace is to be found in the major part of the Zohar. In Safed, this theory was for the first time more fully elaborated and Luria, too, accepted it, though in its own way. The four worlds are: (1) Atsiluth, the world of emanation and of the divinity which has so far been our subject; (2) Beriah, the world of creation, i. e. of the Throne, the Merkabah and the highest angels; (3) Yetsirah, the world of formation, the chief domain of the angels; and (4) Asiyah, the world of making (and not, as some translators would have it, action). This fourth world, similar to Plotinus’ hypostasis of “Nature,” is conceived as the spiritual archetype of the material world of the senses.
Gershom Scholem, Major Trends in Jewish Mysticism; Seventh Lecture: Isaac Luria and his School