Filling cells with Heaven and Earth Qi is not much different from blowing up a balloon; they can expand and contract at any time.
But this isn't the essence of Demon Transformation; expanding and contracting is only laying the foundation. The real core lies in being like a ball, compressed in its unchanged round shape.
The cells won't change, but their quality must change. At least, after the cells are filled with Heaven and Earth Qi, their size remains the same. That's when Demon Transformation and the seventh layer of the Demon Refinement Technique are successfully achieved.
Lin Fei realized that the key to all this is to strengthen one's physique. Only with a strong physique can one meet the requirements of the seventh layer of the Demon Refinement Technique, allowing cells to become a core, storing Primordial Energy without any change in form.
