Refrigerators are so commonly used today in kitchens anywhere. It is necessary for a home to have this appliance to keep food and drinks refrigerated. But what does that mean? Refrigeration literally means to freeze or chill for preservation. Way back before refrigerators were invented, people had another form of preserving their food. Icehouses were used to provide cool storage for most of the year. These icehouses were placed near freshwater lakes or filled with snow and ice during the winter. People tend to invent anything they figure is important and useful, which proves that refrigeration has always been important throughout time. These natural, simple icehouses were once as commonly used as "fridges" today. In the 11th century, the Persian physicist and chemist Ibn Sina, revolutionized distillation methods. She invented the refrigerated coil, which is the main structure of modernized refrigerators, which condenses aromatic vapors. Finally in 1748 the first known artificial refrigeration was demonstrated by William Cullen. Then some decades later, American inventor, Oliver Evans, became known as the "father of refrigeration" for inventing the vapor-compression refrigeration machine in 1805.