Reishi

Reishi (霊子;lit. "Spirit Particles") is the main component of all metaphysically or non-corperal states of matter in the universe. It is said to be the smallest constituent unit of measurement, or existence that spiritual entities and/or materials may assume. It's noted to be adjacent to Genshi - the smallest unit of physical matter in the universe.

Overview
The existence of Reishi is a relatively new human discovery, having been discovered in the Age 698, by the famed scholar, Hashida Lee. The discovery was said to have occurred during an experimentation involving the breakdown, and destruction of chakra. With close examination, as the scientist continued to dissect and study a constant emission of the energy, he'd begin to discover that much like physical matter about him, the spiritual energy itself too possessed sub-atomic structures.

And thus, with his discovery, more and more revelations about the mysterious phenomenon of Reishi began to come to the forefront.

Characteristics
Reishi is by far the smallest state of matter that can possibly be obtained. To put into perspective, the size of a Reishi particle is about 1/10th the size of even the smallest sub-atomic particle that comprises a single atom. As a result, this form of matter is considered to be a very fundamental part of the world's very existence - with scientist predicting that it may responsible for the beginning of existence itself.

Structure
The structure of Reishi itself is one that is both unpredicted, and extremely complex. Just as with sub-atomic particles making up atoms, Reishi come in numerous combinations - allowing for a near unlimited number of ethereal energy sources to hypothetically be able to exist. Overall, to put into simple terms, the different combinations and variation in the Reishi being placed with one another allow for the emergence of different sub-atomic particles, which inevitably allow for a wide range of different properties among their end product.

As a result of this factor - different energy sources, such as natural energy, chakra, and even mana, have been able to exist independent of one another. The Reishi has been acreditted for the creation of other famed spiritual constructs, such as the soul, and it's theorized that certain planes of existence are composed entirely of Reishi, as opposed to the norm which seem to possess an equal amont of Genshi and Reishi co-existent with one another.