The "mother" in apple cider vinegar is a gelatinous substance that forms during the fermentation process. It is a mixture of yeast and bacteria that is responsible for converting the alcohol derived from the apple juice into acetic acid, which gives rise to the vinegar. This substance is often left in raw, unpasteurized apple cider vinegar and is considered by many to be the most nutritious part of the vinegar. It is associated with various health benefits and is often removed in store-bought apple cider vinegars, which can give the product a cloudy appearance. The "mother" is characterized by its cloudy or stringy appearance and is often visible in the liquid. It is recommended to choose apple cider vinegar that still contains the "mother" to obtain the most health benefits.