Jing is a more elusive type of energy and is not simply produced by the refinement and transformation of chi energy. It is much harder to feel and direct as it is basically what holds you together. More than energy, it is better described as a force. It is the foundation for life, a primordial force that animates life in the first place, the glue that holds your cells together. It regulates growth and form in the same way as DNA but it is not DNA. It is actually the force that holds DNA together; you could call it DNA chi. Jing is found throughout your entire body holding you together, regulating growth and also the flow of chi and production of ching.
You are born with a finite amount of jing which is stored in the kidneys. It is burned up through life itself and as the jing throughout the body is used up you begin to draw on the stores in the kidneys. When these are all gone it will lead to weakness, disease and eventually death. Excesses such as drug use and high stress will deplete the jing faster while inner power martial arts methods combined with tantric sex, or other specific etheric exercises can strengthen it and make it last much longer. By doing such exercises the jing is not only strengthened but the rest of the body becomes strong and healthy so there are less unnecessary loads on the jing.
Jing is used in the production of sperm and eggs but is not simply a part of the sexual energy. It is another level of substance altogether and without it the sperm and eggs would be infertile. Since we only have a finite amount of jing, every time a male ejaculates or a female menstruates some of their jing is lost forever. This is the reason that fertility decreases so dramatically as women age. Also the rate of Down’s Syndrome babies born increases from (1 / 1500 at the age of 25) to (1 / 32 at age 45). The jing is vital for babies as it is this that gives the base of primordial substance for their growth. When a woman has an already-depleted store of jing, less is given to the egg as the woman’s body needs it for her own survival. The same goes for the man accept that each sperm may still have the same amount of jing, but he will produce less of them. Therefore the age of the father is not nearly as important.
When the jing of the two parents combines, it causes an implosion into the lowest material dimensions allowing a massive expansion of the combined jing.