Kefir

Kefir is a fermented milk drink similar to a thin yogurt or ayran that is made from kefir grains, a specific type of mesophilic symbiotic culture. It is prepared by inoculating the milk of cows, goats, or sheep with kefir grains. Karachays and Balkars are the creators of kefir and kefir yeast. The drink originated in the North Caucasus, in particular the Elbrus region along the upper mountainous sections of Karachay and Balkaria, from where it came to Russia, and from there it spread worldwide. Kefir is a common breakfast, lunch or dinner drink consumed in countries of western Eurasia. Kefir is consumed at any time of the day, such as with zelnik (zeljanica), burek and banitsa/gibanica, as well as in cold soups.

Source: Wikipedia