This may be found in the last collection of Nietzsche’s works, notes, and letters which was posthumously titled: Will to Power. It is not an official piece of Nietzsche’s, but it seems he did plan to write a metaphysical magnus opus on the Will to Power, until that damn horse incident.

There are indications Nietzsche was loosely influenced by new ideas in physics, especially with his understanding of energy.

The Eternal Recurrence, of how I understand it, seems to be an infinitude of infinite variation in which sameness, due to the breath of scope, inevitably infinitely re-occurs.