When cultivators reach a certain realm, their bones and muscles can become as rigid as steel or as soft as cotton. This is the Bone-Shrinking Technique. If their realm is even higher, they can alter their appearance and physique to perform disguises.
If they are even more formidable, they can change everything through the Arts of Transformation... For instance, the legendary Seventy-Two Transformations. Although these are found in popular novels and storytelling, similar magical techniques do exist.
Chen Zhezhe knew that all of this was caused by the fundamental changes occurring in the body after reaching Foundation Establishment, where True Essence acts upon the bones.
Chapter 378