Kefir is a drink with a consistency similar to liquid yogurt, but with a more pronounced, tangy flavor. It has bubbly effervescence and no bitter aftertaste — some call it the "champagne of milk". Kefir grains are a combination of probiotic bacteria and yeasts that are used to ferment milk (including rice or soy milk). The species of lactic cultures used in Kefir are quite beneficial to the digestive system. To make it, you basically add some kefir starter to milk and wait 24 hours, and it is then ready to drink. Kefir starter is available from Yogurt Maker and The Grain and Salt Society.