Three
Three realms are created as absolute potentials are manifest. The first triad is the beginning of nature. It is a continuum of vibrational potentials from the highest quanta of light energy inside of a star to the zero energy of a proton at rest.
The first realm is the Elemental Realm. The triad of potentials saw the creation of matter. The tiny potentials gathered and mixed.
When the potentials accumulated, some patterns became cohesive, some patterns became repulsive. The potentials danced with each other and spiral throughout existence.
Natural law came to pass. Three realms evolved.