Yogurt is a dairy product that comes from milk. In fact, yogurt is essentially just milk with some bacteria in it! Yogurt has Lactobacillus bulgaricus and Streptococcus thermophilus alive and kicking inside it. To make yogurt, milk is heated, a little bit of these bacteria is added, and then the milk is slowly cooled. The bacteria convert the sugar in milk (called lactose) into lactic acid. The lactic acid changes the liquid milk into the solid, creamy consistency of yogurt. People have made yogurt for thousands of years out of milk from cows, goats, sheep, camels, and buffalo!