There are two types of yogurt makers: Electric and Non-electric Non-electric uses hot water instead of electricity. There is a large insulated container where the hot water is poured. Along with this, there is a small container to add milk. This small container is lowered in the larger container. The electric machines feature a timer and a see-through lid. As soon as the yogurt is prepared, the timer turns off the power. You can monitor the fermentation process via the see-through lid.