Cooking is the art, science and craft of using heat to prepare food for consumption. Cooking techniques and ingredients vary widely around the world, from grilling food over a fire to using electric stoves, to baking in different types of ovens, reflecting unique environmental, economic and cultural traditions and trends. The types of cooking also depend on the skill levels and training of the chef. Cooking is done by both people in their dorms and professional chefs and chefs in restaurants and other food establishments. Cooking can also occur through chemical reactions without the presence of heat.