Peeping Flesh and Recognizing Immortals

What is that under the flesh and blood? Is it an immortal bone spiritual root that can absorb spiritual energy and become an immortal? Or is it an autonomic nerve that can operate autonomously even after being separated from consciousness? Or... Is it an abyss of flesh and blood that cannot be peered into? When the people who pursue immortality truly see the truth under the flesh and blood, and discover the truth behind the so-called immortality, they will know. What will be the consequences of betraying the flesh!