Mixing Sun and Moon
A more advanced taoist practice is the mixing of the sun and moon. Breathing back and forth between natural bodies and their corresponding organs energies the body. The energy of the sun can be gathered and and collected in the heart. The energy of the moon can be gathered and collected in the kidneys.
The two most vital blood channels in the body are the aorta and vena cava. These channels can be used for mixing the energy of the sun and moon. The aorta belongs to the artery system which distributes blood outward from the heart. The yang, oxygenated blood leaving the heart has many fiery and solar qualities. The sun energy can follow the blood down to the lower abdomen/ navel area to mix with the lunar energy moving up from the kidneys.
The vein structure withdraws blood from the outside of the body and takes it back to the heart. The vena cava is more bluish and darker blood flows here. It is more yin and lunar in nature. The vena cava can be a mechanism for taking the lunar energy to the navel center.
Harmonizing arteries and veins, sun and moon, yin and yang will create more neutral energy in the body. The practitioner will feel balanced and harmonious with the outer environment. Follow the earth itself for more spiritual hacks on mixing and balancing the sun and moon.