The present book includes four chapters that express the following briefly:Chapter One: This chapter involves an introduction about Kefir and its unique characteristics.Chapter Two: This section provides information on the importance of fermentation process including basics and types of fermentation, factors effecting fermentation, fermentative microorganisms, and effects of fermented products on health. Chapter Three: This section provides information on the chemical, microbial, nutritional, therapeutic, and antibacterial properties of Kefir in addition to vitamin, protein and mineral structure. Chapter Four: This section summarizes the importance of kefir and its characteristics.