On the Table of Fate
The inner planes, also know as the elemental planes, form the basic building blocks of the multiverse. Each plane is a limitless expanses of one the four elements from which our world is created – earth, fire, air and water, floating in the void of the astral plane. The elemental planes are arranged in such a fashion as to be coterminous with one another only at one infinitely small point. This ensures that opposing planes – earth and air, water and fire – have no overlap with one another, while neighboring planes overlap to create the para-elemental planes of smoke, ice, ooze and magma.
At the point of cotermination, however,, the four elemental planes also pass through the plane of shadow, visualized as an infinitely thin line piercing the inner planes. It is at this one infinitely small point in the multiverse, where the elemental planes are tangent not only to each other, but to the positive and negative energy planes as well, that our prime material plane is created.