What is the starting point of traditional fermentation technology in three rounds of biological examination?

It is the history of human eating, which can be traced back to thousands of years ago. The earliest fermentation technology was natural fermentation. People expose food or drink to the air and ferment it by using microorganisms in the air. People began to find that some microorganisms can promote the fermentation process, so they began to study and use these microorganisms for purposeful fermentation.