What are Kefir Grains

"Kefir grains are probiotic gems made up of a combination of lactic acid bacteria and yeasts in a matrix of proteins, lipids and sugars and this symbiotic matrix (or SCOBY) forms "Grains" that resembles cauliflower. For this reason a complex and highly variable community of lactic acid bacteria and yeasts can be found in these grains". (source Wikipedia).