I love cooking, especially baking.
and other food establishments. Cooking can also occur through chemical reactions without the presence of heat, such as in ceviche, a traditional South American dish where fish is cooked with the acids in lemon or lime juice.
Preparing food with heat or fire is an activity unique to humans. It may have started around 2 million years ago, though archaeological evidence for it reaches no more than 1 million years ago.
The expansion of agriculture, commerce, trade, and transportation between civilizations in different regions offered cooks many new
half the size of a half sheet in outer dimension, while other vendors supply quarter sheets that are closer to half the size of a half sheet in flat baking area.
Institutional use.
Commercial sheet pans are used for many purposes besides baking. Kitchen or cooking processes are often designed around kitchen equipment such as sheet pans, presupposing their ubiquity in most commercial food preparation areas. 
In bread baking, especially, the bread dough will often go through several long rest intervals on sheet pans stacked in open or enclosed