In this task you will be given an answer to a question. You need to generate a question. The answer given should be a correct answer for the generated question.

The history of artificial refrigeration began when Scottish professor William Cullen designed a small refrigerating machine in 1755. Cullen used a pump to create a partial vacuum over a container of diethyl ether, which then boiled, absorbing heat from the surrounding air. The experiment even created a small amount of ice, but had no practical application at that time.
when was the first fridge invented and by whom