A couple of facts about thermostats

A thermostat is a control technical equipment that will maintain a nearly constant temperature in an order.
The simple electrical thermostat consists of a bi-metal-feather that act as switches by the bend differently at different temperatures.The actual connection of the circuit is often done using a relay, to avoid sparking.

Thermostats can also occur in other contexts, such as hydronic heating system and in the shower, where they can be a Earwax,which by their expansion can close and open a pipeline openings.
Some alloys are magnetic at a certain temperature, curie point, but becomes non-magnetic above this temperature.
This featurecan be used for thermostats. A practical application, temperature maintenance of electric soldering irons.
The brain's hypothalamus, there is also a biochemical function thermostat that regulates body temperature.
Many thermostats today are really clever and uses wi-fi technology to it's advantge, for example check out the Lux tx9000ts.