There are three heavens, very clearly distinguished from each other. There is a central or third heaven, an intermediate or second one, and an outmost or first. These follow in sequence and are interdependent, like the highest part of the human body, the head; the middle, or torso; and the lowest, or feet; or like the highest, middle, and lowest parts of the house. The divine life that emanates and comes down from the Lord is in this kind of pattern as well. It is this necessity of design that determines the tripartite arrangement of heaven.
The deeper levels of the human mind and disposition are in a similar pattern as well. We have a central, intermediate, and outmost nature. This is because when humanity was created the whole divine design was gathered into it, to the point that as to structure, the human being is the divine design and is therefore a heaven in miniature.
For the same reason we are in tough with heaven as to our inner natures and come into the company of angels after death–of angels of the central or the intermediate or the outmost heaven depending on our acceptance of divine good and truth from the Lord during our earthly lives.
from Heaven and Hell, Sections 29, 30