Excerpt from Inside Zhan Zhuang
"Under normal everyday conditions a portion of this pre-natal Chi would then enter the Kidney channels where it would ascend and be grasped by the Lungs and mixed with our breath. But when one is deep in Zhan Zhuang meditation in addition to that, something very different happens.
What seems to occur is, this pre-birth Chi or Essence, which comes from both parents and certain other karmic factors, becomes concentrated, nurtured, cultivated or cooked, and eventually transformed in the low Dan Tien, called by some the lower burning space. In this state it acts as both the fuel for the ‘cooking fire,’ as well as part of the ‘food’ to be cooked."