Yogurt is made by adding bacteria to milk and then letting it ferment. To start, the milk is heated to 200 Fahrenheit for about 10-30 minutes. Next, the milk must cool quickly to 112 Fahrenheit and mixed with a yogurt starter (which contains the bacteria). After everything is mixed the yogurt needs to be placed in clean containers and incubated for 4 hours at 100 Fahrenheit. After incubation the yogurt is placed in the fridge for approx. 10 days. Final step: eating your homemade yogurt!