Body Reconstruction, 환골탈태/脱胎换骨 also called as (Phantom) Metamorphosis, is the state in which the body of a master will emit a bright light and the bones and muscles will start to break and reconstruct into the best version of the body in order to suit the martial arts prowess of the user. The process ends when the skins begin to crack like a "shell" and turn to dust.
This process is important to martial artists as it signifies that one has reached the end stage of their current realm or moved up a new realm in their cultivation.
It can return the appearance of an old master regress to a younger state.