Qi exists right after the formation of individual life. This kind of qi is inherited from kidney-qi of the parents during pregnancy. So it is called "congenital qi" which is the foundation of the development of new life.
After birth, the human body keeps absorbing nutrients from the external world to nourish the congenital qi. This is the acquired source of qi, also known as "acquired qi "Acquired qi originates from food nutrients and fresh air in haled into the body.
In fact, the "congenital qi" and "acquired qi" are just two material sources of qi. The process of qi production also involves the other viscera. The inter-transformation among essence, qi, blood and body fluid influences the production of qi.