Sub-Atomic
The subatomic level of our elemental-physical body blueprint commences at the first layer of our "core manifestation template". This "template" is the 1st dimensional layer that consciousness utilizes to manifest in the physical worlds. Also, this first layer is at the 1st Dimensional level of the Earth plane and its energies (Chi) are synthesized and transmitted through our bodies via our Root Chakra or 1st Chakra.
Reference
Term first found in HGS Manual: Page 116