Any wannabe molecular gastronomer should know what the Maillard reaction is. All chefs use it, often without realising. It’s one of the essential reactions in cooking and is responsible for almost every (non-artificial) cooked flavour you’ve ever tasted. Essentially, all foods contain a plethora of amino acids and normally a couple of naturally occurring reducing sugars. When the food’s heated, sugars and amino acids react together and form literally hundreds of different flavour compounds, giving a whole spectrum of flavours and aromas. These compounds then slowly break down into even more different flavours and aromas (which is why some foods actually taste better the day after they’ve been cooked).
The Maillard reaction is also why seared steak and flame grilled kebabs taste so good. You can see (and taste) it in toasted bread, condensed milk, roasted coffee. Surprisingly, the same reaction happens (albeit more slowly) in wines and champagnes. Either with or without heat, it also tends to turn foods that nice well-cooked brown colour.
So, chemically, reducing sugars contain a reactive carbonyl group which reacts with the amino group of the amino acid (in an SN2-type nucleophilic attack), forming N-substituted glycosylamine and water. The glycosamine then undergoes Amadori rearrangement to form ketosamines. An alkaline environment further catalyses the process by deprotonating the amino groups. The variety of chemical compounds this creates are not actually particularly well characterised, though a number of articial flavours are made using a similar process.