The pot-in-pot system is an appropriate technology. Appropriate Technology is a technology that is practical. It must be easy to construct. They also need to be constructed from materials that are available and made by local people. Pot-in-pot was developed in Africa. It was created for people to store food for longer periods of time. There are two pots, a small pot inside of a larger pot. Between the two pots there is sand, and when water is pored on the sand it makes the inner pot colder. This is used like a refrigerator to keep things cold.