Qi Refinement

In the cultivation world, the Body Refinement Realm wasn't even considered a true cultivation realm but rather as a mere starting point. 

The purpose of the Body Refinement Realm is to strengthen the physical body and establish a foundation for the cultivator to retain Qi within their body.

As the cultivator progresses, they will enter higher realms such as the Qi Refinement Realm, the Meridian Opening Realm, the Foundation Establishment Realm, the Core Formation Realm, and beyond. Each realm brings new opportunities for growth.

 Without a solid foundation it becomes difficult to progress further. Therefore, it is crucial for cultivators to prepare themselves thoroughly in the Body Refinement Realm before moving on to higher realms.

For Chen Tian, it wasn't a problem, as he had the best foundation in the cultivation world history. With the Chaos Body and the Chaos Dantian, Chen Tian had a natural advantage in the Body Refinement Realm.