Introduced to the Romanian food market a few years ago, kefir, keefir, or kephir, alternatively milk kefir, or búlgaros, is a fermented milk drink made with kefir "grains" (a yeast&bacterial fermentation starter) and has its origins in the north Caucasus Mountains. It is prepared by inoculating cow, goat, or sheep milk with kefir grains. In this video, you can see the yeasts (the round forms) and the bacteria (dots and rod-shaped forms).