People have tried to keep cool or keep their food cool for ages. The chinese invented ice cream 4000 years ago , and they kept it is snow in underground chambers. In baghdad in the eigth century a king imported snow and put it is the walls of his summer home to cool the home . in 1884 , Jacob built a machine to make ice in London. The first home refrigerators appeared in the early 1920s since then , people have preserved their food in refrigerators . about the same time , air conditioning if large spaces became possible . since that time , people have cooled themselves with air conditioners in store , offices , and home