The Inner Planes surround and enfold the Material Plane and its echoes, providing the raw elemental substance from which all the worlds are made. The four Elemental Planes — Air, Earth, Fire, and Water — form a ring around the Material Plane, suspended within the churning Elemental Chaos. These planes are all connected, and the border regions between them are sometimes described as distinct planes in their own right.
At their innermost edges, where they are closest to the Material Plane (in a conceptual, if not a literal, geographical sense), the four Elemental Planes resemble places in the Material Plane. The four elements mingle together as they do in the Material Plane, forming land, sea, and sky. But the dominant element exerts a strong influence on the environment, reflecting its fundamental qualities.
Farther from the Material Plane, though, the Elemental Planes are both alien and hostile. Here, in the outermost regions, the elements exist in their purest form: great expanses of solid earth, blazing fire, crystal-clear water, and unsullied air. Any foreign substance is extremely rare; little air can be found in the outermost reaches of the Plane of Earth, and earth is all but impossible to find in the outermost reaches of the Plane of Fire. These areas are much less hospitable to travelers from the Material Plane than the border regions are, and as such, these regions are little-known. When discussing the Plane of Fire, for example, a speaker usually means just the border region.
The creatures usually called elementals dwell there, including the Elemental Princes (primordial beings of pure elemental fury) and elemental spirits that spellcasters can bind into galeb duhrs, golems, invisible stalkers, magmin, and water weirds. These elemental creatures don’t need food or other sustenance on their home planes, because they are sustained by the elemental energies that saturate those planes.
At the farthest extents of the Inner Planes, the pure elements dissolve and bleed together into an unending tumult of clashing energies and colliding substance, the Elemental Chaos.