When was tea invented?

Tea, an infusion of herbs (flowers, leaves, stems, roots and/or bark of plants), in boiling water, ingested for medicinal use or as a beverage for re-hydration or simply for the taste has been around longer than man has been keeping written records.

Tea, the herbaceous plant grown for its leaves as a cash crop has been in cultivation for centuries.

The original "inventor" was Nature itself. Humankind twigged to the use very early on (I think they were still dragging their knuckles in the dirt at the time)